Originally Posted by yorxs

Started having problems with the engine revving to 1500RPM in neutral or in between shifts. A search of the forum conclusively indicated bad throttle body. Ordered the 74mm upgrade from Needswings and the problem totally went away. However the check engine light came on the next day, and I'm throwing P0171 & P0174 lean codes.

Double checking my work, but not finding anything obvious, but certain it is related to the work I just performed and not faulty O2 sensor(s).

Any with advice on how to troubleshoot?