Get it (:
www.mx6.com will be your friend.
There isn't much aftermarket support for the 1st gen (88-92) MX-6's. Too bad it isn't a GT, much cheaper to make faster. There is a j-spec engine, but you need to change a lot of stuff...probably not worth it unless you can do it all yourself. And even then...my advice is always to buy a GT.
It's like the one in my sig, right? What color is it, condition, and auto/mtx? DX or LX?