I put a pair of the Jones Exhaust mufflers on my SPF about a year ago. They're pretty much the same thing sold by Classic Chambered since their Cobra mufflers are just a glass pack. They are definitely much less restrictive and louder than the stock SPF mufflers. I wasn't looking for louder, but with the 3" core, they certainly are. So far, so good. Here's the link:
https://www.summitracing.com/search?...ord=JEX-A4324S
Ted