I have ab '05 RX8 (112K miles) with rough idle ... typical I guess. The dealer wants $821 for a "tune up" to fix the problem including new motor mounts. This can't be right ...

 

It's not. Do a search for rough idle. Try to do it yourself and save a ton of money. If you don't work on your own cars, check around for prices. People here will be more than happy to show you how to change your coils, plugs, etc.

 

If you're not comfortable doing it yourself, you could even make a post in one of the club regional boards. I'm sure someone's pretty close who will help/show you how to do it for a few beers.