I've owned three 6.9's. My first two were non-turbo and my current truck has an ATS on it with 4" exhaust (no muffler, glasspack, ect.). My first had a C6 tranny with 4.11 gears, so 60 mph was about it (even with 35" tires ... lol). My first did pull a semi and trailer weighing in at 78,900lbs. down the Bend Parkway at 25 mph without a problem (Amazed the truck driver and everyone else that drove by). My second had a 4 speed manual, but I wasn't impressed with the manual in all honesty (I hear the ZF5 is a better manual to go with). My current truck pulls like a dream (before it decided to have a bad day on me). I pulled a steep grade up out of Prineville, OR with a 1,550lb trailer and a '74 Nova on the trailer at 60 mph all the way up and was backing off the throttle because I was getting closer to 65 mph at the top. I reccomend the turbo. Don't get me wrong... My first two still did well, but blew alot more black smoke up the hills. I have 3.55 gears in mine and I get 20 mpg (highway) and 18 mpgin town with LT315/75R16 tires. This combination shocks people when they see just how fast this old heavy 4x4 can get up and move (even with the trailer behind it). I'll stay with my old diesel despite the fuel prices rather than buy some Honda because "There's no replacement for displacement".