I have read al the posts. Granted changing mufflers, fooling around with mid pipes will gain SOME power.
But if one is SERIOUS about power gains, they need to consider longtube headers. There is no free lunch.There never has been. The stock exhaust system on the 3.7 is more than adequate for the application. Sure, getting louder mufflers and maybe a mid pipe will free up a few horses. But it is a piston engine. And replacing stock exhaust manifolds with free breathing tuned headers, has always been what is required , when wanting maximum power.
So, change your mufflers, get a new mid pipe. But if power is what you really want, why dink around, start with a good set of headers, and build from there.
As for cost, it NEVER was cheap to get power. So don't expect a muffler change, to turn your car into a pro mod,
On a stock 3.7 any exhaust modifications will help. But you always had to get headers first, regardless of the application if you were serious, about power.
Sorry, just had to comment.