Just bought a 92' Miata, had a rough idle but I replaced spark plugs, PCV, cleaned the idle air control valve and throttle body, rough idle is fixed and now idles smooth around 900rpm, but now if i rev the car or pull up to a stop after driving the idle will be high and only come down to about 1,300-1,500rpm. What could be my issue! Thanks!
(I have the idle screw all the way down)

 

Have you checked for any vacuum leaks yet? there's a good chance that could be your issue