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94 C1500 4.3 to custom built 358ci 400hp using original,beefed up 4l60e. Original TBI from 4.3 and original electric EGR valve with machined adapter plate. Truck runs Very well. The problem is Check engine light on, egr code, you can’t play with the HP, full throttle will put the truck in limp mode.
 

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Original TBI from 4.3 and original electric EGR valve with machined adapter plate.
Are you saying you're using the same throttle body with the original injectors for the 4.3L on your new 358 ci in? Did you do anything with the PCM (tune) after you changed engines?
 

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Get yourself a 5.7 computer and chip. The 4.3 is way off for this engine, including starving itself with the 4.3 throttle body. At a minimum, get a 5.7 throttle body. And a tune.
 

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I have a 5.7 +40 over (358ci) with the 5.7 TBI, computer, and chip, Melling MTC-1 cam, and a fuel pump for a ‘96 Vortec 5.7. Totally good. You need some more fuel.
 

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  • I have a 5.7 +40 over (358ci) with the 5.7 TBI, computer, and chip, Melling MTC-1 cam, and a fuel pump for a ‘96 Vortec 5.7. Totally good. You need some more fuel.
    Thanks for the information. I’ll start working on it and keep you posted.
 

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Are you saying you're using the same throttle body with the original injectors for the 4.3L on your new 358 ci in? Did you do anything with the PCM (tune) after you changed engines?
Would Summit Racing ECM with a Hypertech street performance chip work?
 

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Maybe, I'm not a big fan of "mail order" tunes. 1st, I would check to see what PCM you have. If it's the 16197427 (most common for 94 -95 trucks) you should be good for the bigger engine, just swap the memcal. Here's some info about the 7427 PCM with all kinds on .bin files etc. There are guys on gearhead-efi.com that can "burn" a chip for you or you can go to a boneyard and find one. Using TunerPro RT and a Moates Ostrich2 you can data log and tune your own - lots of research to do but, it's a lot of fun.

 

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I played with a Hypertech chip several years ago in my ‘94. Same size engine I have now. I really never noticed a difference. Perhaps it was just the 4.10’s that hindered things because of the sheer weight of the xcab long bed 2500 frame. I don’t know.
 
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