The symptoms I have felt sound just like others on here. Maybe I'm not going so fast because my T'bird has a sidecar on it. Still seems to crack on OK though.
I'm interested in the heatwrap, although the heat seems to be coming from the top of the engine. What is the wrap and where did you put it?
Since it's not often hot here in the UK, and if I stick my right leg out a couple of inches the problem dissapears, I guess I'll probably leave it as it is.