thanks ill see if i can get them to send me a tune and how much and all cause i went to Louisiana to see my sister a couple weeks ago and with them running 80-85 the whole way down there i only got 16 which i guess is ok just seeing if i can pick up a lil
On the highway I can get 20-21 out of mine with +10% larger tires. I'd probably also get 16mpg if I raced at 85. I try not to drive much over 75 for long trips. Most speed limits where I go are 70, so barely over that keeps me out of the way of traffic and nets me decent economy.
Get yourself a lighter pair of shoes and you're mileage will increase.
As for local tune, ask around some of the shops if they do, or know of anybody who uses HP Tuners. They can then tell you the cost. I was quoted well over $200 to get started on mine. The guy didn't have any credits to get into the system, it requires 2 credits at $75/ea, so right off the bat I'd be paying $150 for the credits to allow the software to talk to my PCM. He was just an independent dude who did this in his home garage on the side. Somebody who does it often may have 'money in the bank' and can get into yours for cheaper.
Also take into consideration that 2wd Z71's are tuned differently than yours, so those individuals will see less harmful performance effects with the same size tire as you.
Good luck.