the voltage outputs from a AFM (1.6) and MAF (1.8) are the exact opposite.
so without electronics know-how, it's not going to happen.
The RX-7 AFM (B series) is an easy swap and dyno proven to add some gains for N/A miatas, although I wouldn't just throw one on without tuning with a wideband.
plus it looks like you lose a bit of mid range and peak torque, which isn't fun. I'm running 12psi on the sotck AFM. It works. Unless you shell out for a piggyback or ecu that can remove it, it's not really worht the trouble IMHO.