My 89 trans am GTA gets about 12.5 miles to the gallon. Wich is not very good obiviously, now its not stock , it has a 383 in it with high flow fuel injctors and some other stuff. But someone recomended a "Dyno tune" to me. Now i am pretty new to all this, but can someone tell me what these things do and if they would help my MPG.

Thanks

Nate