Here's my definition of competitive based upon my experience driving a spec muffler class Yahama Kart:

Competitive is when you're not spit out the back when the green flag drops, and you're not lap traffic for your class after five laps. Given this definition there are lots of Spec Miata that aren't competitive in their own class. I found I needed a new Kart chassis and to blueprint my motor to not get left behind, my best finish was a 2nd place because I drove a smart race and didn't get collected.

James