I have an 04 na 3.3L with 190,000 on it. Trying to figure out which route to take for parts. The lean code could be a ton of problems. I have a OBD2 scan readout of the Fuel trims for starters. The O2 sensors all seem to be within normal operating conditions. The Bank 1 seems to be the issue hence the P0171. Short term with start at 0 then drop to -25%. I think that is because the Long term is stuck at 35.7% no matter what, cold start/ idle, 2500rpm....etc. MAF sensor reads normal so not sure that is it. The issues are; possible vacuum leaks, fuel pressure drop, fuel clogs all make sense for numbers fluctuating out of range in Short term and Long term readings or even bad numbers being read on both bank 1 and 2. Im Lost. I should mention, the truck runs slightly rough at idle.... little shaky. Its perfectly fine when the load is applied. truck starts and runs. No excessive fuel consumption that i notice. truck has original O2 sensors, cats, MAF and injectors. going to try to spray some card cleaner around engine to measure the ST LT readings again. The odd thing is the LT bank 1 fuel trim being stuck at 37.5% no matter what.