I really didn't think changing the fuel filter in my GLI would make much difference, particular seeing as the fuel inside the old filter looked perfectly fine. But wow, after a couple days, what a difference. I'd had some slowly-worsening issues with throttle response, particularly at low speed -- starting from a stop while engaging the clutch, or accelerating at low speed in gear. The car would bog a bit and then surge, unless I modulated the clutch and gave more throttle than I really should. Those problems immediately went away after the fuel filter change. This was at 55,000 miles. I think I'm going to have to start changing the fuel filter at about 40,000.
Pros: improved throttle response, fixed bogging and surging
