Never mind got it covered,

 

I have a 05 wrex and i have a helix up pipe with a hks bov. During shifts I run rich at times thus causing a fireball sound to come out of the exhaust. If you decide to get an ap to prevent the fireball problem it won't do squat to a aftermarket bov.

As for sound I have a apexi catback and helix uppipe installed and it has a nice rumble to it, not too loud or quiet. Especially if you decide to lower your car like I did my car seems a bit louder because it's closer to the ground.

I don't have an ap, but i believe if you get up and dp catted or non-catted you do need some kind of engine managment, but if you decide to just get an up pipe you don't need one.

 

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