Just got done my new MBRP 4" exhaust, with cat delete pipe and MBRP muffler. Sounds good but is there much difference with or without a muffler? The MBRP muffler has no baffles-you can make a fist and stick your arm all the way through. I was just curious how much louder it would be with no muffler at all

Mine is straight piped and there is quite a bit of differance, not so much in the low-end, but when you romp on it it's definitely louder. Not so loud that it is annoying, but it sounds really good IMO.

mine was 2 dB from stock: http://www.dieselplace.com/forum/showthread.php?t=385385

now it's noticeable under acceleration, but I don't really care around town, i just did not want a drone on the highway like my dads's 6.0PSD with turbo back.

I guess there's not much difference then. Mine makes a light rumble at idle but gets loud once you get into it. The turbo makes a cool kind of hissing sound at idle-kinda sounds like a semi truck at idle. I guess I could always just pull the muffler clamp and take the muffler off and see for myself