At CM when you were telling me about your 80's power loss I was vaguely remembering my beater '99 S70 Volvo from college. Back then, for a few weeks it suffered (some) power loss (though it never had any to start with). And it had a strange hissing noise that would come & go especially at higher revs (2500+). I eventually find that the 🐈 had become clogged with a fat hairball (unburned fuel from frequent short trips to college/home) for whatever reason. But as you were telling me I didn't think it could be the same since my Volvo didn't have the overheating symptom.
My Volvo had an electric fan that would turn on/off based on the engine's temp sensor. If stopped at a red light for 20+sec, it'd turn on and it sounded and felt like a jet engine if I had the windows rolled down. And it'd very quickly cool down the engine!
Not quite the same symptoms or the same platform, but still. I should've remembered my Volvo and mentioned it. Lolz. There's a lot of lessons I learned and should do better to share.
I thought you had put an electric fan on your 80 in addition to the regular belt fed. If you haven't... You might consider scavenging a fan from a 90s Volvo sedan
I'm totally willing to help out.
Allen