I think I remember that you had a bunch of trouble at the Pros in yours with axle hop, etc. Maybe that was someone else, that's pretty much ancient history at this point. I never did a Pro in that car, but we had great luck, 100% stock w/M030 and BFGs, at regional events and at a couple of Tours. After I won AS at the '98 San Diego tour I expected a lot of people to buy Boxsters, but pretty much no one did until the 2.7 came out. I wish we'd taken that car to Kansas. Only big loss I had for the one season we raced that car was to our own Andy Bettencourt at Devens in '98, if memory serves. But that was a serious horsepower course with a drag-race start. Boxster lost a second right at the start.
Anyway ... you would know better than me about costs, being in the Porsche world, but I assume that body parts and engine work is pretty expensive ... but I don't really know.
I'd love to see a Boxster in ITR. I think it would make a great race car.