Hi. Twice now, a few months apart, after keeping my Evo 9 in the garage for a few days I start it and get a P0171 CEL (lean). I cleared the code and the car runs fine. The A/F gauge does not show anything unusual. Has anybody experienced this issue? This has never happened when the car is actually running for a while, only during cold starts.

 

Check for vacuum leaks first.

 

Boost leak test. If that checks out, look for a leak on the intake pipe.
If that checks out good, look for exhaust leaks before the O2 sensor.

 

All good suggestions. Thank you!