I removed my muffler and there really isn't any restriction to flow - There are just fin like baffles on the sidewalls in it that catch some noise, u can look straight through it. Does give it a much louder turbo whistle and sounds like a big block when u romp on it.
Ran mine with a strait pipe for awhile, when I went to the 4", turbo back, .. didn't like the sound. Put a MagnaFlow on.. Didn't notice Any EGT or or performance loss/gain, never have. Makes a cool, throaty, powerful sound... I like it. Even better now, with 150K+ on it.
