I have a 95 6.5 TD and am only getting about 11 mpg in town. I dont do any highway driving, just in town but I'm pretty sure I should be getting better than this. Whats wrong?

95' K2500 6.5L TD
6" Pro-Comp lift w/ triple hoop shocks, 35x12.50 Pro-Comp Mud-Terrain, 15x10 Weld racing rims, skidplate, K&N filter

If you don't find out here you should try the Diesel Page, I think the address is http://www.thedieselpage.com

That's bad, you should get 18 about all the time. Unless you got a powerchip and a leadfoot? Oh and 18+ on the freeway/highway.

Rice burner's suck! Go Bigblock!!!

Well the first thing you need to do is quite putting gas in your diesel engine. Oil burners do not like gas.
With 4.10's expect about 14-16 in town, add +1-2 mpg ea for 3.73's and 3.42's. I get a low of 10-13 pulling my travel trailer, city 15 +/-1, a best on freeway of 18.2 from Seattle to Portland and back going 55 mph with cruise on. Otherwise I'm topping out in the 17.x range.
Your timing could be off, -1.94 is the best, injectors could be bad or dirty, injection pump not working correctly. Dirty/clogged fuel or air filter. Bad fuel, I have noticed differences between brands, and get better mpg's when purchased at one particular station here in town by over 1 mpg. Where do you live. You may have winter blend in the stations near you. Winter blends give you less BTU's per gal, hence less fuel mileage by about 1-2 mpg's, depending upon how much #1 is in the mixture.
Marty