I put one of these air filters on my new P5 and it seemed to make a difference. I'm just curious whether anyone would know how much actual horsepower or torque gain there would be. The guy who sold it to me said about 10%, but of course he'll say something like that. I just wondered if anybody had firm evidence of what a better filter could produce. Thanks.

 

if you're talking about the drop-in replacement filter for the stock airbox, I doubt it makes any measurable power gain. maybe slightly better throttle response, but that's about it.

 

I have one of these and I can't say I gained any HP but I agree that the throttle response is better.