Hi, I have a 2002 Audi A4 quattro 1.8t, ive gotten the code p0171 system to lean (bank 1) and I've had is also read that there is a misfire from cylinder 4 at one time and cylinder 2 at a different time. somedays the car works fine without a problem but on somedays when i try to accelerate even somewhat aggressively the car lags, bogs and seems to skip. please help thanks