I have a 90 rx7 it smokes when it starts up and for a whille after it warms up i was told to change oil injectors for intake made no differance.
my trans wouln't shift into overdrive i changed the lock out solenoid on the trans the button on shifter isn't bad but it still won't shift. The hold light flashes after you start driving when just sitting still you can push the button and the hold light will turn on and off but after you start driving the light just flashes and it won't shift into overdrive.

 

Smoking a bit at startup is normal for older motors, trans sounds like a problem if you care about it. You will probably have to replace the trans.