I replaced the stock muffler on my LBZ with some straight pipe (an old stock exhaust) today. I tested EGTs before and after I got rid of the muffler. It doesn't help at all, not even 20 degrees EGT. It looks like the big restriction is the CAT, followed by the 3.5" stock pipe size. It does make the truck sound a little better, but it's not really any louder. The CAT does most of the quieting AND the restricting.

Just wanted to pass this on for anyone thinking about it...

ANy sound clips of this?

the cat is the biggest restriction. get an lb7 front pipe and you will probably throw codes. a fingerstick and egr blocker is what you need, at least that is what worked on my buddies lbz.

EGR Blocker and fingerstick are an easy install and less black smoke. $50 gets you the kit at kennedy diesel. Nothing to loose In my opinoin. Catless sounds great.
Jerry

Full exhaust (turbo back) arrives tomorrow. EGR blocker and Fingerstick coming...