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?

 

Did you replace the MAF sensor housing with the larger one, and INSTALL the OLD SENSOR into the new larger MAF sensor housing?


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I was able to locate the cause of the problem. On the top of the throttle body is a nipple fitting that accepts the rubber T with the hoses connected to it. While visually it looked to be installed, I was able to push is down tighter onto the throttle body with a long screw driver, thus making a tight seal. Air was probably leaking past when it wasn't push all the way down onto the throttle body. The check engine light stayed off today and I feel the idle smoothed out a bit.