Cars without roofs = death trap. Miata is a great platform as they are light (sub 2300 pounds), tons of parts available for cheap and low compression engines that love boost. Buy a stock turbo and run E85 and you can get 250 WHP without touching the bottom end. If you are a decent driver and have a 250 whp miata not many cars unless the are radical builds will be passing you. Cars are safe also as they have full roof.