this is most likely an all time noob question but I'll ask anyway. Which between these Magnaflow and Invidia Q300 exhaust 1) is louder and 2) makes the most HP and torque gain?
I heard sound clips of both and they both sound like they would not be obnoxiously loud.

 

Ironchef I believe dynoed maganflow and got 10whp. Invidia was between 10whp-12whp so the difference is extremely small, not enough to tell a difference.

Loudness, I have never heard of either in person, but Black Betty has Invidia and NJlakeshoreG has the magnaflow exhaust, you can PM them for more questions.

I would go with Invidia for better quality IMO