99 system too lean

I have a 99 tahoe fuel pump, pressure regulator, and filter have been replaced, now getting engine codes po171,174 system to lean bank 1 and bank 2:banghead: please help

Pull out your mass airflow sensor (square block with a 3-wire connector plugged into it, spliced into the air intake pipe next to the air filter box) and do a visual inspection through the screen on the sensor. You should see 3 tiny little resistors- be careful- they've very delicate. i had a situation almost identical to yours. In addition to what you're describing, the vehicle also would bog and lose power after driving for a while.

Anyway- you can spray off the resistors with some throttle body cleaner or some electrical parts cleaner. Don't pull the screen off the sensor, just spray through it. If you have a scan tool with data stream capabilites, you could watch the mass airflow sensor and see what it's actually measuring. Put it back on and road test it and see if it corrects your concern. Dirt on the resistors can cause lower than actual air flow reading, resulting in driveability problems.

I also might suspect false air. If you have any air leaks after the MAF that is extra air that is not monitered by that sensor. Check all the air ducting carefully and check for vacuum leaks.

thanks guys will try your suggestions this weekend and let you know