Truck won't twist tighter than 2500rpm

[BradyYoung]

Alright, so all of a sudden my dads truck will not turn 2500+. He drives a 2002 2wd psd. The truck is all stock except for a magnaflow muff and we put an old superchips gold chip in it a few months back. He had been pulling an inclosed gooseneck around the austin area for a few thousand miles, but these issues came up about a month after any hauling. The truck still responds well driving around town and on the highway, but if you pull out to pass power dies off at 2500rpm. Anyone ever have the same issue? I'm stumped... the superchips gold chip wouldn't be enough to hurt it? would it?

[azkcr]

First off, sucking all that dirty air from that hell-hole called Austin wasn't good for it. I keed, I keed.

But it's hard to know precisely what's going on until you hook a computer to it and run diagnostics.
-Oil pressure (high pressure side) could be low, resulting in poor injector performance.
-Not getting enough fuel, clogged filter
-If he has been keeping his foot in it while towing with the Superchips on, it could have caused problems
-Cracked/ leaky/ popped-off intercooler boots.
-Turbo is dying or dead. (Heat from the towing + superchips could have warped the exhaust fins. Air won' push flat fins)
-About 100 other things could be going on

If it's in town (Bryan), there are some guys around here that can look at it.

[BradyYoung]

Well his truck isn't showing any MIL or CELs but I haven't had a chance to look at it yet. He hasn't noticed anything like a hose or boot, but I'm not sure he has had a chance to really check anything out yet. The truck isn't here, they live in Abilene.

[azkcr]

CELs are referred to "idiot lights" for a reason.
Because by the time they come on, it's too late and you feel like an idiot.