Four sounds right. Airbox to turbo, turbo to ic., ic. to intake tube, intake tube to throttle body.
Though... there is the one for the idle valve too.

The intake leak wasn't really intermittent though, it was more like I drove like a grandma all the time, so it wasn't apparent until I tried to really push it. There was a time when I drove in high winds and noticed it wasn't able the keep up speed without constantly spooling the turbo. It did pull okay for a while, but not really well at all. I think it just degraded slowly into undrivable. It was not awesome and then crap and then awesome.

I've replaced my fuel pump because it went bad. The in tank pump was bad for a long time, and eventually the main pump died too. It sounded like a hornets' nest for months and always worked, until one day.... nothing. Dead as a doornail.

I'm guessing that the power stage/amplifier/ignition unit on the firewall is not overheating at this time of year. How about water getting into somewhere like the distributor?

I'm thinking right now you could just pick and pull another ECU more easily than track down all these other possibilities. I've learned to listen to my hunches. I would check the idle air valve hose just for kicks though.

good luck,
Will
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1990 740 Turbo, on its way to stock specs, maybe beyond