Inconsistent CEL and discreet squeek
02 WRX 143000 miles. My CEL has come on and gone off again 4 times in the last 3 weeks. I dont have a blinking cruise light. It seems to me that the car is producing alot of exhaust fumes (relative to other cars). The code for the CEL was a cylinder misfire. As far as i know the car has an aftermarket downpipe and exhaust. A wrx knowledgable friend drove the car and said its "running rich"?? Also there is a very discreet very high pitch (non rotational) noise coming from the left side (not sure if its front or back) of the car when i make R turns. This does not seem to happen at low speeds, and i wouldnt be able to hear it at higher speeds. Incase you havent noticed... i know nothing about cars. Any positive input would be greatly appreciated. My friend who has owned 3 wrx's drove it and said it drives like a champ.