I have a 1995 Mustang 3.8 vert. I have a mil light on and code po171 (lean bank) is what the scanner prompts. This is a car that I bought for $500 with a bum trans that sat for nearly three years. Got it running in Jan 2007 and it runs great except for that code. Coincidently, the motor sometimes idles at 1000rpms before kicking back down to around 550rpms. It will do this many times but there is no notice in performance just the annoying code and idle. I do know that the hoses that go to the purge flow solenoid are dry rotted and I will replace them this weekend, but is there anything else this could be? I know its not the maf or I would have codes for both banks.