Lift pumps
 

Could anyone of you tell me whether or not a bad lift pump will produce a readable code?
:w2:

My 98 never gave a code until I had to give bosch $3000 , my 05 never gave me a code. Just started acting funny. Best thing to do is check the pressure, mine was down to 9 lbs injector pump over heats, spend to much money.

The first signs you'll see is a random drop in boost, in the upper rpm's, it might seem like the truck is "laying down". Like South Texas Goat said, check your fuel pressure at the rear of the filter, it should be around 15. Best way to tell though is after changing the fuel filter, it will struggle to get fuel back to the engine.
Hope that helps some.