I hate to take this thread too far off topic, but because the D was made in 1981, CATs are required in all 50 states. Just because some states don't check, doesn't mean it's legal to run without them. You could technically get ticketed at any time for using this system. Granted that doesn't happen often, but it's possible. It's why the system is labeled "For off road use only".
But somebody could buy this at a good price, purchase new CATs and still come out at a lower price then a new system. So it still can be a good deal for those that want one. I would do that if I didn't already have a DPI Spec 1 installed.