Hey all, I have a VERY loud 383 with SLP shorties to Flowmaster AT w/ a high-flow cat. Don't get me wrong, the car sounds bad@ss but so loud that I need to half-yell at my friends even at idle. After searching a lot of posts I decided to order a pair of Flo~Pro Twister 18"x4" round mufflers and insert them right before my exhaust tips. I checked for clearance and there is just enough. At only $40 each I thought it was worth a shot. Plus, installing them at the tips it's a simple clamp-on.

I will let everyone know how it turns out.

 

They have the spiral design. Here

 

Well I put them on, a total of 2, and let me say wow! To have a 383 sound this tame is awesome. It's still loud and deep but not obnoxious like it was before. I compared the noise level to my friend's cammed '94 LT1 (w/o cat) and his idle was quieter but when he revved it to 2k and 3k, his was waaay louder then my 383 (w/ cat) at the same RPM (before mine was so much louder)

Plus, I park in a garage underneath my house (basement), and before the entire house would shake even at idle. Now house doesn't shake anymore

Worth $40 each... HELL YEAH!