Should I go through PCMforless I had the loudmouth exhaust, cold air intake kit from K&N and a 160 thermostat. I just installed the thermostat and I notice a difference some cars love it my friends camaro has a 160 but he said my car responded so much better!! It revs like hell and I was at 60MPH and punched it and it drifted alittle to the left when I hit 80MPH and my car never does that! Car runs at 170F.

How much improvement in gas and power with a tune?

 

Anywhere from 0-15 HP is my guess.

 

I don't foresee gas mileage improvements, as for power gains, 10-15rwhp gains are possible.