I am trying to tune a 99 GMC Denali, first 5.7 I have ever done. Does anyone have a tune file they would share to help me out?

 

What are you trying to achieve outta the tune? More power? That is pretty simple - decrease the PE Enable timer to .5 seconds, eliminate the engine brake torque management, increase timing by 3* for everything over 1200rpm. I can't remember what else off the top of my head, but if you're interested I can look over my old truck's efilive tune I put in it.
For mpg, you're gonna have to data log to get the most out of it, well at least that's the way I know. Tuning the shift points and TCC lock up to better suite the driver's driving style is huge, and setting the DFCO to accommodate the driver's habits will help some (it's much easier to tune the dfco on the 5.7s then the newer ls pcms in my experience)

 

One other quick note - I did nothing with my trans tune from a performance stand point based on the fact it had the 4l60 in it... I just changed the shift characteristics during part throttle. Search the hp tuners site/forum for more help