Bought my second LS about a year ago with around 100,000 original KM. It had been neglected from the previous owner(s). The project has been on hold for many months. I just started working on her again. I have since cleaned her up pretty good and completed a major tune up with Motorcraft: battery, alternator, coils. NGK spark plugs, Fel-Pro VCG's, oil pan gasket and serpentine belt. Cleaned throttle body, K&N air filter, MAF sensor, oil change. -When I start the car and the RPM's drop to idle around 650-700, the vehicle shakes. If I give it some gas it will go away. - Accelerating with a light throttle past 2000+ RPM feels like it hesitates and doesn't want to go any higher. It will just stay there, unless I press harder on the gas pedal, then it will jump up a bit then shift. The problem seems to not be as bad if I really step on it. The following codes shows up with a KOEO using Forscan: U1131 - Lack of fuel pump status response U1262 - SCP Data Link Fault (IC and ABS) C1805 - Mismatched PCM and/or ABS/TCS Module C1963 - Stability Control Inhibit Warning P1233 - Fuel pump driver module offline My research has pointed me towards the secondary fuel pump or jet pump. Before I go and replace that. Do you think that is the culprit for the U1131, P1233?