ive been wondering this for a while... whats up with pics of people just having an airfilter strapped to the tb? im assuming it isnt MAF, but how does it work and what is it?

 

The system with the airfilter on the throttle body is SD (speed density).
SD uses a sensor to measure intake manifold vacuum and computes eng load from that (and other parameters).
SD does not directly measure the air mass entering the eng.

The earlier TPI systems used MAF (mass air flow) sensors to help determine eng load. Around 1990 or 1991, the TPI systems switched from MAF to SD.

 

but don't get excited, that air cleaner mount right on the Tb is a good way to loose power, just think all that great hotter than hell air coming through/off your radiator being sucked in your engine... not exactly an improvement...