Service Engine Light - System Too Lean (Bank 2)

Hi All, Thanks for your time.

I have a 2001 V-6 mustang that had the Service Engine Soon light on last week. Checked codes which turned out to be System too Lean (Bank 2).

Took it to a dealer to have it diagnosed. Dealer called back with a $685 quote claiming MAF sensor and an HEGO sensor is bad (Mass Airflow Sensor Defective Baro 147 Hz, HEGO sensor Bank 2 Out of Range).

Did some research online on the MAF sensor getting dirty and decided to try cleaning them out before spending $$$. Declined the dealer quote and asked not to change them.

Guess what???? When I got my car back, Service Engine Soon was not on Checked my codes again, no errors... I am guessing there was some loose connection or the dealer cleaned it out. Have any of you come accross a situation like this....The guy at Autozone said sometimes a bad fuel can wack the system out...

Lately, when i start the car it usually idles high at 1500 to 2000 rpm for like 5 seconds before it comes down to around 1000 rpm...Also, when I shift gears the rpm stays the same rather than going down when i engage the clutch..Any findings?????????

Thanks again for your help...

44,500 miles