Foot Well Heat

My 99.5 A4 2.8 Quattro (85k mi) occasionally generates a lot of heat in the driver's side foot well. I don't know if this occurs on the
passenger side. It occurs with the climate control absolutely off an utterly deactivated--no heated air is issuing from the foot well vent(s). The surfaces in this area clearly feel warm, as though engine heat is excessively penetrating the firewall.
It only seems to happen after extensive driving, but even then only seemingly sporadically, which is a puzzle. Some days after extensive driving it occurs, others it does not, I think--I've not done a scientific study. It also seems to only be perceived when the outside temp is above about 70 deg F.
Anyone else have this problem? Sometimes it is so uncomfortable I have to turn on the A/C.
I seem to remember somebody in the Audi newsgroup reporting this problem with an A6. Dave
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