I have a 01 2500 4x4 6spd when i first got the truck 2nd hand it had the stock lift pump installed my first mod was gauges i noticed my fuel pres. was 10psi @ idle and WOT was 0 psi so i then installed the FASS system and my fuel pres. was 15-17PSI at idle and 11-12 WOT . I then installed a full banks system turbo exhaust and programer . ran great good fuel pres. and 40lbs of boost now its 6 months later and i can only achieve 31lbs of boost and my fuel pres. does not change from idle or WOT and it use to smoke when i was on pedal but not much smoke now it does this on a cold or warm day and i also had my MAP sensor replaced would any one have any suggestions where i should start to look for my problem to get my truck to the way it was 6 months ago ?