I can get an '88 turbo or an '87 turbo, should I hold out for a '89+?
 

Right now I can get a '87 turbo for 2800 and a '88 turbo for 3600. I know '89+ has a bunch of improvments, but if I get my wish it will eventualy have a new engine in it. What do you guys think? Rx-7's are rare around here.

get whats available, fix it up, sell it when you find a later model if thats what you really want.

Yes, the 89+ models have some improvements, but they also have some liabilities when compared to the earlier models. You mentioned a new engine, so what is your goal? Is there anything in particular that you like about the newer models, such as the tail lights, front end, etc? I kinda agree with Icemark, and think that you should just buy the first car that you feel fits your needs, and don't worry so much about what year it is.

Thanks for the help, I was wondering...this car has turbo, should I buy an aftermarket computer for it? I'm assuming yes and also, can I get any shop to tune my turbo.

No, just worry about the things that need to be fixed first, such as leaky fuel injectors/pulsation dampeners, fried wheel bearings, locked-up driveshaft, brittle vacuum lines, worn weather seals, worn shifter bushings, and the other usual 2Gen stuff. You can go plenty fast with the usual "ghetto mods": High-flow fuel pump, high-flow air filter, high-flow exhaust, fuel cut defenser (FCD) & aftermarket boost gauge. I recommend that you change things as they wear out or when you find a good deal. An aftermarket computer costs $800-10,000 and tuning it usually runs around $500-3,000 at a professional tuning shop. If you can afford this, then it is a wonderful upgrade, although it is not necessary unless you make radical changes to the engine.