The exhaust on my 99 RS has been making some funny noises. It's been sounding like a backfire almost, sort of a loud thud... I though it was something in my trunk rolling around back there but it turned out to be the exhaust. It only does it when I'm starting from a full stop in 1st or a rolling start in 2nd. I swapped out the airbox for a cone filter not too long ago, could that be to blame? I know the Subaru's with MAFs don't like intakes, but it seemed to run fine before. If anybody has experienced a similar problem or has any insight your help would be greatly appreciated. Thanks.

 

You just have an intake, no exhaust mods? I could perform that backfire on demand when I had my borla headers... Downshift to first when coming up to a light, the light changes, gun it... BOOM! Basocally you are dumping extra gas that goes pop.