I've tuned my friends 04 Suburban 5.3 and he loves it and I'm gonna start tuning my buddy's 05 GMC 1500 6.0 here soon and will keep in touch through this thread on what I find works best. I may start with my pirated Quadzilla stealth 2 tune - but looking at it I can already tell the trans portion needs some work. One quick tip is that when you raise the governor you need to play with the trans tune, it is set up to never go into 4th at WOT. It is set to shift into 4th at 8100 RPM yet the rev limit is around 6000 so you should lower it down to 5600 or so so that you can shift into OD and keep on pushing over 100. I like the WOT 2-3 and 3-4 to be set at 5600 (what the stock 1-2 shift is).Other than playing with shift points, torque reduction and a few other engine limiting safety features I just plan to advance the timing a bit, possibly starting with the Quad's timing table and building from there based on SOTP feeling.