I have a 99 sierra and a 02 silvy both have 255 lph walbro intank pumps my sierra has a nelson tune and i mentioned that i had one, would he have modifyied something in the tune for it? I have no SES light on everything works great! now when my stock pump went in the 02 silvy i decided to put a 255 in instead of stock and this one has no tune bone stock other than air intake. As soon as i started the truck a SES light came on i got it scanned it said Very high fuel pressure or vacumm leak, then evap system leak!!! WTF now i have 2 bad o2 sensors on drivers side... my buddy has EFI live and we could not find anything on tuning for fuel pumps... there both return style fuel systems! Also another problem just happened to the 02 i have to wait for the truck to build pressure before starting it, i replaced the fuel prssure regulator and it still wont hold pressure. Bad Pump? any imput would be great i need to get this thing right its getting about 11 mpg right now and gas is killing my wallet! My 99 modified truck gets about 5 more mpg than this gas hog!

thanks

 

No tuning for the pump.

 

damn thanks for the imput!