Hi @ Speedster986,
Welcome to the group! Careful about "Scratching that itch" on this mod. MPG on this car is a tough nut to crack.
I dare say your computer has a 'glitch' in it. It seems to be almost impossible to get mileage that good.
Best I have been able to achieve is around 26-28 MPG BUT, having said that, I DO NOT drive anywhere near conservative. If you have this car you are obligated to drive it accordingly. In order to get mileage that high you must be unde-revving it. My wife borrowed my car and got over 30 MPG (per manual calculations) but I found out she was DOGGING it!
Doctor's orders are: Upshift UNDER 3k until warm…then NO LESS than 3k on upshifts after that. You may cruise at less than 3k, but IT IS a sports car and I think that widening the TB or intake WILL ALLOW more air and gas mix in - using more, not less gas.
I have a 4" intake on my car and IT HAS GOBS more power but not much better gas mileage.
Most people here would agree the POWER is more important than MILEAGE but opinions vary so you are welcome to try. Keep us posted!