94 K2500
6.5 TD
Vin F
Remote mounted PDM, new top end, new T-chain, GM4 turbo, 99 water pump, duramax fan.


I’ve been semi restoring this truck and I’ve rebuilt the top end of the engine with new heads, and an newer model water pump, rebuilt the trans, and rear end.

I’m not trying to make a super truck, I pulled a camper from Delaware to Montana and back last summer and I’d like to do it a couple more times. I take it easy on her and have a good set of gauges for trans temp, egt, and boost.

My problem is with my boost control. It worked fine after the rebuild. I switched back and forth between a mechanical boost controller and the stock system a few times just experimenting a bit. Then I ran the manual controller for the last year... I decided to switch back to the stock system again to take a quick trip to VA and get a good read on towing fuel mileage as I never did leave it stock long enough to compare. My problem is it’ll boost when I first accelerate but immediately drop off to 0psi. If I let it back down to idle it will build vacuum back up to the wastegate. The vacuum pump is holding 25in the whole time this happens. I replaced the wastegate solenoid, intake air temp sensor, map sensor on the intake manifold (not the one the firewall).

I don’t mind just switching back to the mechanical spring and boost fooler but I am wondering if this is exposing another problem. I’ve always thought I was slightly under powered and if the computer is deboosting, it must think that it needs to and maybe it defueling as well. I have a hard time deciding if it is underpowered as I know these things aren't power houses and I don't have any experience with any other similar vehicles.

I’ve wondered if the computer needs to relearn after having the boost fooler on it. So I have taken it on several short trips the last week but nothing has changed

If nobody has a better suggestion, I’m going to take a real careful look at wiring and ohm check them from the sensors to the computer. I might be able to take it to my buddies shop and put a scanner on it to see data.

Otherwise there are no codes and it runs pretty well with the manual controller on it.