Installed my AS & M headers on my '01 2500 HD 4x4 6.0 yesterday. Took about 4 hours for installation. A few minor glitches along the way, but overall, very easy to install. Found out that you have to cut about 1 inch protrusion off passenger side of the transmission where it bolts up to engine. It doesn't serve any purpose, so no harm removing it. Everything else is very straightforward. Be forewarned on the HD's though, when connecting the headers to the rest of the exhaust system. When I talked to AS & M techs prior to buying these headers, I asked how much work it was to connect them to the rest of the exhaust system. I was told it didn't require much at all. It ended up taking the exhaust shop 4 hours getting the headers connected to the rest of the exhaust, so it's not a cheap proposition. The exhaust guy is a perfectionist, so that was part of it. As far as the sound, it sounds awesome! It actually quieted the truck some over the stock exhaust manifolds, but sounds very good, especially at WOT. I didn't do a before and after dyno, but the butt-meter tells me it made a decent improvement.

Jason

 

i just put mine in and my exhaust guy was pissed at me cuz the headers didn't line up so well he aswell had to do some work to make them fit haven't driven it yet though ..hope it's worthwhile mod with my supercharger gettin the fans slapped in at the same time <img border="0" alt="[cheers]" title="" src="graemlins/gr_cheers.gif" />