error codes PO102 & PO305

P0102 is the Mass Air detecting low input. the most likely cause is the mass air sensor. this lives in the intake tract, just before the carburator or throttle body (depending on configuration of your intake)

P0305 is a misfire of the #5 spark plug. this will be caused by a coil if each cylinder is connected driectly to a coil and not to a distributor. Back in the days of old, there was a distributor that spun around, and a coil that had to charge and discharge thousands of times a second -- tens of thousands of times if the motor was running at high speed. engineers found that if there were several coils, then the charge cycle could be stabalized, and the coil could be triggered by the computer instead of by contacts inside the distributor. This makes for a better combustion cycle, and lower emissions.

Some engines uses a coil for each spark plug, others use 3 coils for 6 plugs. Either way, a misfire in a particular cylinder is easy to detect, and all you need to do is replace a coil to solve the problem.

Alternatively, if you actually have a distributor and a single coil, then you have a crappy plug wire. This is a cheaper problem to fix, I think. Get good wires ...