Twisted Smog Diagnostic Isolator

An EGR Diagnostic Isolator for 1988-1997 Ford trucks and Broncos with EEC-IV ECUs :

We are currently take pre-orders for the Twisted Smog Diagnostic Isolator. We are waiting on labels for the new product, and anticipate that we will be able to ship orders no later than the 20th of January.


These diagnostic isolators are designed to temporarily separate the SMOG, EGR, and corresponding vacuum sensors from the ECU so you can easily isolate a sensor issue.

If your EGR system is suffering from a sensor or component failure, your truck will run in the EEC-IV “limp mode” – resulting in horrible gas mileage or your truck running dangerously lean. This isolation tool will allow it to run without the SMOG and EGR temporarily, without going into the “limp mode”, so you can then safely isolate and identify where the problem is coming from. This will allow your ECU to run the engine solely off of the needed fuel injection sensors and components. This is for temporary use, and cannot be “installed” permanently in your vehicle.

Using the same approach as we take in our vintage stand-alone harnesses we are now able to do a full EGR, vacuum sensor and smog system isolation for 1988-1997 Ford trucks and Broncos. This unit isolates and partitions off the EGR sensors and components in a way that allows your engine to only run on the needed fuel-injection components. This allows the ECU and engine to operate temporarily without the EGR and SMOG components. Additionally, our tool kit includes the belt to bypass the SMOG pump allowing you to diagnose if the problem is coming from the SMOG pump itself.

You can then easily reconnect your vehicle for SMOG compliance.

** If you are needing to on isolate all of your SMOG tubing, purchase the SMOG pump tubing isolation hardware bundle option **

** Before you Buy : It is highly recommended that you fully read the instruction manual fully prior to purchasing to understand what this tool does, why it does it, and what the scope of the project is beforehand. **

Included with this kit :

  • Twisted Smog Diagnostic Isolator
  • EGR valve block off plate
  • Serpentine belt needed to not turn the SMOG pump
  • All connectors and mounting hardware
  • Shipping + Handling Included

** Attention : If testing the SMOG pump itself is not needed, you can purchase the diagnostic tool without the belt. **

5.00 out of 5 based on 11 customer ratings
(11 customer reviews)


SKU: twi-smog Category: Tags: ,

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Additional information

Twisted Smog Engine

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11 reviews for Twisted Smog Diagnostic Isolator

  1. 5 out of 5


    I couldn’t be any happier with the quality of product and service Russell at the 460 EFI guys offered. The throttle body swap and Twisted Smog install were smooth and have made a remarkable difference in performance and function. Along with added power and a more responsive engine, there was a large trash can full of useless, in the way, parts that were able to be removed. Highly recommended modification.

  2. 5 out of 5

    (verified owner):

    Super easy install comes with everything you need literally cut wires and hook them up and enjoy no smog engine makes it alot better.

  3. 5 out of 5

    (verified owner):

    Amazing results, tons of noticeable power. The intake manifold really let the motor get air and breath. The smog delete blockboff kit, produced tons of power not having to push that horse power robbing smog pump and exaust gas air.
    Thanks Russell for all the awesome products, and all the continued technical support with your products. Even though it is a work in progress, it is well under way to being restored.
    460 EFI guys really know how to turn the 460 into a tire ripping beast.

  4. 5 out of 5


    I installed the Twisted Smog on my 1991 F-150 and could not be happier! The instructions were easy to understand and the install was very straight forward. I have noticed improved performance and fuel economy. I am very impressed. The only downside is that I am not seeing the fuel economy increase anymore because the improved performance has turned my foot into lead. I would highly recommend this product to anyone.

  5. 5 out of 5


    my engine ran smoother than it ever has, i also noticed it picked up power and doesn’t smell like it’s dumping fuel. Thanks, from Casper Wy

  6. 5 out of 5


    Hooking up the Twisted Smog box could not have been easier. The directions are clear and straightforward. I hooked mine up and it was good from the start. No codes at all. Even if I had trouble, Russel does a great job of taking care of customers and has been a wealth of knowledge answering many questions for me. This is one of several items I bought to upgrade my 1995 F350 and I could not be happier.

  7. 5 out of 5

    (verified owner):

    Twisted smog delete box is worth every penny. No more lack of power, no more studdering, & went from 6.7 to 9.6 mpg on the 1st tank . As for the belt on a 95 f250 with ac after a few slung belts it wound up being 95.5 inch belt with 2 3/8 flat washers on all 3 alt bolts between the alt & bracket! But you can see the geometry for the idler to belt is wrong so i ordered a delete bracket & proper pully from ebay which should fix that problem & it was less than 60.00 shipped . Unlike the 99.00 bracket that you still have to buy the ac delete pully for to use the stock belt. & Russ was a big help ! Highly recommend.

  8. 5 out of 5


    I have this in my 1995 7.5l truck and it runs great! Thank you 460efiguys for helping me make my truck come to life.

  9. 5 out of 5


    Before my twisted smog I was averaging 7 mpg on the highway in my 93 f350 crew cab long bed. After the twisted smog I’ve been averaging 12 mpg at 80-85 mph on the highway. Couldn’t be happier with Russel and his customer service.

  10. 5 out of 5

    (verified owner):

    460 EFI Guys came into the picture after the breaking point… when I gave up all hope on this garbage 1991 EGR/SMOG crap and ripped it all out. I wanted to retain EFI – but was about to put a carburetor on it I was so angry.
    The truck idled at 2k rpm and NOTHING would slow it down. I felt I had ruined my truck and was carb shopping when i found the website.
    Enter 460 EFI Guys… I installed my Twisted Smog kit and the truck IMMEDIATELY ran ALOT better… but the idle was still ridiculous…

    Enter Russell: This guy took time out of his day to call me and troubleshoot my truck over the phone!!! We pinned down that the ECM was toast.
    With a new ECM, the Twister smog kit, and all the other garbage gone, this little 302 is a tire burner! And now it only has 6 sensors total!!! SO EASY TO WORK ON>>> HUUUGE improvement in this truck!!!

    Another brick nose saved from the junk yard. I drive it every day now.

  11. 5 out of 5


    I currently have this kit on my CCLB 1995 F350 with the 7.5l engine. I could instantly feel the power increase. I appreciate that the 460efiguys took the time to properly eliminate the smog garbage on these trucks. One of the best aspects of this kit is that I could eliminate the rats nest of emissions hoses and garbage that made it difficult to work on this truck. Now there is plenty of room. I feel confident that this is the way that Ford SHOULD have built the truck.

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