Exhaust
 

I wanted to know how much HP the SLP Loudmouth Exhaust adds. Is this a good choice or is there another system that would do better?

Your probably gonna see maybe 7-11, it's good for the price.

Catback wont really add any power. Maybe 5 at the most.

What would be good for under 500 bucks?

Not really...you would be paying more for sound...which is worth it for most people...If you want a performance mod...I recommend getting gears.

New midpipe and headers will give you 15-25rwhp.