171 174 code 2002 flex fuel tahoe

i have a 02 tahoe LT im getting the 171 and 174 bank 1 bank 2 lean codes after replacing intake gasket, fuel pump, fuel presure regulator, spark plugs, wires, air filter, fuel filter,throtle pos sensor, MAF sensor,and o2 sensores. im getting frustrated cause i cant seem to find the problem and neither can 2 different mechanics. can someone give me a idea what else i could be cause im bout stumped :banghead:

i have a 02 tahoe LT im getting the 171 and 174 bank 1 bank 2 lean codes after replacing intake gasket, fuel pump, fuel presure regulator, spark plugs, wires, air filter, fuel filter,throtle pos sensor, MAF sensor,and o2 sensores. im getting frustrated cause i cant seem to find the problem and neither can 2 different mechanics. can someone give me a idea what else i could be cause im bout stumped :banghead:


with these codes and your work completed so far I would look at the crankcase vent system for leaks,,,these hoses,,PCV etc...may be your problem...oil fill cap,,,oil dip stick seal etc,,,

any air ducting leaks after the MAF will also cause this...

There is another thread somewhere in here that somebody mentioned that the intakes can warp and continue to cause a vacuum leak even if new gaskets are installed. This should be easy to check with a smoker. Wherever the smoke is coming out is where it is leaking.