Posting this to get a little info. I'm not sure what was exactly done to this truck as it's just one I adjusted the idle on, but I saw it had banks goodies on it and that peaked my interest. I've driven some 12 valve trucks that have been played with and was impressed, however this one I worked on today you couldn't even get the turbo to spool up brake torquing it. I took the truck for a drive and leaving from a dead stop it was a big pooch. The boost didn't come up until 2500rpm + and then it would go up as high as 30. If you kept the revs up it had fairly decent power, but if the rpms were below 2000, forget about it. I didn't ever notice any excessive smoke. I might add that the egt's really shot up until the boost finally kicked in. The customer showed up to pick the truck up and I quized him a bit. He did mention something about a plate (injection pump mod I presume) and that he had a turbo put on. On inspecting the turbo I looked to me like the stock unit with the exception of the 1/2 of the turbo that attaches to the exhaust manifold. That looked like it was different, but the air charge side looked stock. He had also mentioned that the torque convertor had been replaced with a Banks unit (which felt like it had an imbalance or loose torque convertor bolts at idle, noticeable shake at idle, especially in gear, but engine ran smooth). It also had Banks exhaust, but only the 3.5". Any ideas? I'm not the one thats going to fix the truck as he said he's taking it back to banks, but I'm curious as to what could cause this. School is now in session.....

 

I know that you would have caught this, J Body, but it sure sounds like a turbo boot problem except that it eventually builds boost. I had a boot come loose and it would "eventually" build to about 20 pounds.

 

The turbo is too big for it.
Make him give you the stock one.
The shake at idle/ in gear may be a bad injector.