I am having a problem with my 1999 A4 1.8T Quatro. My car is bogging but not everytime I drive but most. I have changed vaccum lines and fuel line this past week run's good for a few miles, butthen it occurrs again. When it happens the carboggs and when I push the gas pedal it get's worse to the point the car stalls. PLEASE HELP! NEED SUGGESTIONS! MAYBE IS THIS THE FUEL FILTER?