I'd agree that in general the suspension/tire setup vastly outweighs any engine mods in an autocross. In our case we have an easy metric - SSC. As I see it, until I can run with the best SSC cars driving is number one and the suspension is number two on my agenda.
I'll probably end up doing the engine this coming winter, just because I have most of the parts and I'm tired of people asking if the engine is running when we're in grid
