2500HD 6.0 help

I bought a 05 2500HD with the 6.0 and 4.10's about six months ago. The power isn't too bad, but it could use a little more at times when I'm pulling a 24' stock trailer. I've only got about 6000 miles on it so far and gas mileage has been everywhere. Pulling 15,000 lbs I know it gets less than 10. Driving around the farm is anywhere from 9-11. I have actually gotten 14-16 strictly on the highway, which I didn't feel was too bad I guess. My question is, are there anyways to increase mileage that actually work. For instance a different muffler, intake system, pcm tune, etc. I've read about the nelson tune, but I nervous about installing it and having problems with SES lights coming on and stuff like that. I should've ponied up the extra dough for a Duramax, but I'll probably only put 10-12,000 miles on a year and didn't feel it would pay for itself. I would also like to dump the 245 tires on it and go to a 265, but I don't want to lose anymore power or get any less mileage either!

All of those things would help. I would go with the Nelson, I have had it since last June and have never had a problem. If you do Allen will work hard for you until its right. Def. worth the money, and it will wake that 6.0 right up. It woke up my 5.3 by leaps and bounds and I have gotten 1-2+ mpg's

Good luck trying to get more mileage while towing. Your unloaded mileage is normal. You're right...shoulda sprung for the duramax for very heavy loads on a regular basis.