Kurt,
When someone pokes a hole in the rules, we have to figure out how to tighten the rules, plug the hole, and limit the "change" cost to existing racers. Spec-ing 1 plate only would be the simplest solution, but costly to many people. When you look at the majority of plates our racers actually have, they're pretty similar. So take the commonality among them and change the rule to limit costs to the majority of racers. Make sense?
Another point is that any parts outside the rules can be sold off to 944 Cup racers, or to the guys racing 944's in Australia, or to ST class 944 cars. This is what we did back in 2004? when chips and headers were making the cars noticeably uneven in performance. We had no HP cap then. Most guys affected just sold their Stahl, MSDS, Bursch headers, bought stock ones, and put the cash difference into their next entry fees. Some guys actually left the class because of this rule change, but honestly, if they didn't want equal cars, they didn't belong in this class did they? And the class has since quintupled in size and spread across the entire country. Proof positive that the 944 Spec idea of having to outdrive, not outspend the guy next to you on the grid is a formula that attracts and retains racers. Just give racers an affordable chance to win and the rest is up to them.