I recently changed my WRX air filter with a basic paper purolator air filter. After the install I noticed that when I really get on it, I hear a whooshing sound like air is escaping from a vacuum. I had some trouble getting into the air box and the stock intake popped out. I placed it back in and sealed everything back up. The filter is in correctly and I am not throwing any codes. I only hear the noise under hard acceleration. So...no problem? The old filter was caked with crud so maybe it is just breathing better? Any thoughts would be appreciated. Thanks.