Drove the K20 to American Muffler and had exhaust installed. The system is 3" pipe from the headers to the x-pipe, then 2 1/2" to Dynomax UltraFlo's and continues as 2 1/2" pipe dumping at the rear of the flatbed angled down slightly. The truck is running pretty rough, back firing or missing - now that I can actually hear the motor it sounds like a timing issue and a rocker or two need to be adjusted. Here are some pics of the system. This is the X-pipe that I had built by someone I found on E-bay. Rather than use the collector piece that came with the headers, American Muffler made their own piece The passenger side collector was fairly close to the transfer case. Here is a pic of the pipe coming over the transfer case Here is the X-pipe installed directly behind the transfer case And here is an example of the welds at the X-pipe Here are the Dynomax mufflers Pretty straight shot to the rear of the truck The pipes dumb right before the hitch and are well protected As the motor is running rough I have not gotten on the gas to see how the system sounds - will have to wait to see what is wrong with the motor.