After upgrading ECU last year, was looking for a little more power....my a4 was up for timing belt change/tune, so I purchased a timing belt kit from ECS Tuning, AFE dry-pro drop in filter, and decided to purchase an 034 HFC as well (mine as well get the mechanics to put it in while they're doing the timing). Dropped the filter in myself first...no change in feel other than some additional turbo noise on the high rpm end.

Got the car back today and love the new HFC...notice a lot smoother pull through gears 1 - 3...less "jerkiness" from turbo kicking in. Definitely feel more torq and overall power. Great investment for those thinking about the HFC.

 

what would be the difference between the HFC and a Test Pipe instead?
Thanks

 

Test pipe has not cat...it is straight through exhaust disposal. HFC maintains the catalytic converter to filter out the bad stuff from exhaust.