I was playing around yesterday and I had left over 6 nuts so I though I would try them. I bolted the exhaust up to my heads with no problems. They are the same size as the stock (expensive) nuts and twice as beefy. Has anybody else used these on a running motor?

They should work as long as you can tighten them.

Those look suspiciously like 911 cam tower nuts,as they're awfully narrow to be exhaust nuts (which are 15mm O.D., wider than the 13 mm wrench size nuts that are supposed to go on there). Probably about as wide as the flange on the stock 2.0 exhaust nut, though. No reason why they won't work, "IF" the stud isn't too long, preventing the Allen key from being able to fully tighten the nut.

The Cap'n