My boost isn't quite what it should be either; though the weather hasn't allowed me to tear into the truck yet, here's what I've read to check (roughly in order of highest probability first):
-Up-pipe donuts. The turbo gets its power from the exhaust; the up-pipes carry exhaust gasses from the exhaust manifolds up into the turbo collector pipe. The pipes have "donuts" that seal them and these are common failure points. Any leakage here and the turbo won't spool up.
-Boots between turbo and intake manifolds. Since these are under pressure, any cracks or loose clamps will cause leaks.
-Loose intake manifolds
-Low fuel, possibly due to clogged fuel pressure regulator (FPR) screen or clogged fuel filter.
-Sensor failures, such as the MAP (manifold absolute pressure). Best determined by a code reader (the ones at Autozone WON'T read our codes)
-Clogged EBPV sensor tube (this has been debated but seems to be a possibility)
-IPR leaky orings (but often is characterized by poor warm starting)
At 176k, I wouldn't expect the turbo to be worn yet unless the air filter has had sealing problems and the truck has been driven in dirty conditions. Well, actually the stock filter does have issues with sealing, so most of us have upgraded to a real air filter such as the Tymar, which flows more air and filters better. Still, I'd be surprised if your turbo is shot at only 176k. (Garrett is the stock turbo.)
