TBI Chip and 3:42 gear setup

[88 GMC Truck]

I have a quick question for you. It seems that I have been unable to get a straight answer from anyone about this question. I hope you can shed some light on the situation.

I have a 1988 GMC C2500 350 TBI Vin K Truck with a 3:42 rear end and the 700R4 OD trans. I have the old EPROM (Hypertech) chip which was for a 4:10 gear setup and which came with the truck new (the Gears 4:10) .

Does anyone know where I can purchase a chip designed for the NEW Setup I have now >>>3:42 Gears? Im Stuck on 14 MPG and I just replaced the engine which has an R/V cam now. The Eprom # 1227747 LO5 88 GMC 350 TBI final drive codes, are different now. The Hypertech Chip which was purchased back in 1990 when I had the 4:10 rear end gears, was a Stage 2 Chip and had a GT5/GT8 code number indicating the 4:10 gears. The new gears I have now, use a GU-6 Code number for the ECM Prom Chip.

Does anyone have an answere to this technical question about what chip to use ? Also what MFG would be best to go with Jet Vs. Hypertech ??

Im hopeing to get better miliage out of the right chip seeings that with my old and new engine the miliage is exactly the same 14 MPG Hwy and city!

Thanks !

[2000CAYukon]

There are some places that do custom TBI chips to address your setup.

www.pcmforless.com
www.tbichips.com
www.turbocity.com

There are more. Do a google search on "custom tbi chips".
Not sure how much they can improve on the mileage but they should be better than stock programming.

//2000CAYukon