i have a 99 cummins and install comp about month ago lost my lift pump after then installed tha fass pump only it gets louder/wierd sounding when put down to full throttle seems to run fine at idle and when babied it dosent seem to be vavle lash but i am checking the valves soon thought maybe injection pump but there is know dead pedal also maybe lifter but never really sounds bad idle or injectors but dosent miss or smoke also getting 380 miles to tank of petro and thats babied any thoughts would be appreciated

 

Need a little more info please Got gauges preferably fuel pressure?
Describe the sound youre hearing Squeel? knock?Rattle? growl?
might have to unconnect the comp box and try without for new test.

 

are you getting much black smoke? the 380 miles to the tank is quite suspicious,even if you filled around the 1/4 tank mark it is still 12-14mpg I trust you already looked for any fuel leaks, now look for boost leaks. pull the codes

 

well....i'm getting 15.7 m.p.g. same as when it was stock....no air in the lines or what not, good pressure. just gave up trying to fix it.

still better than my chevy 3500 with the zz 502 crate engine