Possibly a leaky injector?
 

Seeing as how an rx7 is fuel injected, they usually take a few cranks to start.. But recently ive noticed (once in awhile), when starting my 7, was that it fired on litterally the first crank. (When this happens the idle usually sucks for a little while also) The only conclusion i can draw from this is that there is a tiny amount of fuel either in or leaking into the engine.

So my question is, is there an easy way to check for leaky injectors? Or do I have to pull all 4 of them out?
Or is there anything else that might cause this?

Thanks,
Nigel

could be leaky injectors or bad compression. check the FAQ if you need more help.

Fuel injected cars should fire almost immediately. Some systems require a crank or two in order to figure out the position of the engine but the RX-7s ECU receives enough "home" signals that it basically knows the position of the engine any time.

At this point, most of the RX-7s take some cranking to start because they are out of tune. This is likely your problem. :) A full tuneup does wonders...