Your intake/EGR port is probably gunked up. See this -
http://www.miata.net/garage/manifold/index.html
It's easy to DIY. Get a couple can of intake/throttle body cleaner and go to town. I used some weed-eater line to make sure the little EGR port was actually cleared out. You'll understand after you see the link above.
Maybe 4 wheels aren't so bad after all... wickett.org
It only goes to show when people can no longer discriminate on the grounds of race, religion, or sexual orientation, they can improvise and still find someone to hate. - Dave Moulton