1998 3500 6.2 with 6.5 after market heads , new pdm oversize turbo, seperate mapp sensor regulated at 5.5-6lbs [ to trick computer] runs 12-14 lbs boost and runs great under 65mph all day long BUT after 65mph pump timing goes back to tdc or limp home mode , this appears to be speed related. maybe im over thinking this,but could use some help. i dont want to buy a new computer if i dont have too, 500$ is not in my budget. -

im pretty sure that map sensor trick is not working all the way. why not get or make a turbomaster and a potentimeter boost fooler to run another couple of lbs of boost. it will be a band aid until you can get a computer reflash. got any pics of your turbo? -

Woody35's Sig:

1997 Chevy K1500 4X4 EC/SB L56 6.5 Liter Turbodiesel
9.5 Inch 14 Bolt Axle ,3.42 Limited Slip Posi, 4L80E Tranny, HD Tranny Cooler,
265/75R/16 UniRoyal Liberators A/T
2005 VW Passat TDI 2.0 Liter Daily Driver
1938 Allis Chalmers Model B
MODS: Straight Pipe, and Metal Step
Dynoed at 12.5 HORSEPOWER

I have a turbo master on turbo, when this happens i still have 12-14 boost but injector pump goes limp, but dont get any codes or lights. working on the pics -

how much boost are you running at 65 mph.

are you running something like this

Boost Fooler Instructions -

at 65-70 around 9-11lbs pulling hills 12-14lbs but my map stays at 5.5-6 have put guage on this, once i pass 65 the injector pump retards and i must shut it off for 30-40 seconds then im fine till i pass 65mph -

have you checked all your eletronic connections to make sure there tight. just to clarify you can flogg the living crap out of this truck below 65 mph pulling 14 lbs of boost time after time but as soon as you hit 65 it craps out. it sounds like the engine is defueling because the intake air temperature (IAP) is too high. has this happened once, twice, rare occurence? also how were you accerlating to 65? -

cold comming down exit ramp like grandma, or hot like im going to a fire [just so happens i am, fireman that is] checked all the wires that aint in the harrness. should have good cold air but my iap could be at fault, if it is what should i look for. and yes regular like clockwork , can i read this sensor like a themistor [spelling aint my strong point] with a meter. -