Do I need a Madza compression meter to check the compression?
 

Or will a regular pressure gauge like those used on a piston engine work.

And if it will what should a 1991 N/A read at sea level?

Thanks, I nhave the entire wiring harness disconnected, can I still use the key to turn the engine over? (the starter is still connected).

Sounds easy enough, so what should be the reading in PSI?

85 is the minimum. 125 is the max you will ever see.
The mazda tester is required for really accurate results