Ideally, I want use of the "Engine Signal Monitor (49 9200 162)" and adapter (49 9200 163) listed on page 4B-31 of the FSM for 86-88 turbos. It's the thing that you plug in between your ECU and harness that looks like it would make troubleshooting much easier.

Does anyone know where I might be able to find one of these things? Would a dealer have one and if so would they ever lend one out?

 

Try a Mazda dealer. It's what's called a Breakout Box. You might find the equivelant at http://www.toolsource.com/ost1/results.asp?qu=breakout or at least that site will give you a good idea of the price of this type of equipment. Big Bucks.

An alternate means is to buy a busted ECU and use the jacks on it plus the plugs off the harness of a wreck, to make your own. Labor intensive hobby/thing to do.

Or you can use wire taps to tap into the wires that are of the most importance to you and monitor the signals that way. That's also a flawed idea in that once you remove the wire tap you have a opening in the wire insulation that must be repaired at sometime.