Ah ok, what muffler is that? I'll give it a try. As for the pipe size, it has 3 1/2 inch exhaust stock and I'm adding the longtubes, I also have a bigger cam, and may add a cold air intake so I'd want to get setting that flows good and is somewhat noticeable but not to obnoxious since it is my "Dad mobile" lol I plan on addi g a electric cutout somewhere in the exhaust for when I want to show off lol. I just didn't know if 4 inches would be overkill, some say that going too big affects back pressure but idk in new to these LS engines.