I recently bought an 1987 FC N/A and when I turn it on the idle will rev up to about 2,000 then drop down below 1,000 and maintains a weak idle which sounds as if it is about do die. Any suggestions on what I could do to fix this and is it normal for Rx7s to rev that high after you start them?

 

The car is supposed to rev to around 3K for the first few seconds (7 seconds?) after it's started, then settle down to 1500RPM, which gradually drops to the final 750RPM idle as the car warms up.

Your issues are probably due to vacuum leaks and a misadjusted TPS. Could also be a problem with the BAC valve.