High-RPM Stumble : Motronic Spider

[GV27]

Hey guys,

New problem discovered on my Spider. When the car is really hot I get a high-rpm stumble. At 4500+ RPM it "hiccups" once or twice going up through the range. Seems to loose power completely for just a split second. It'll stumble just once or twice between 4500rpm and 5500rpm. This occurs only when the car is nice and hot - like after I get off the interstate, sit in traffic for a couple of minutes then head up the hill towards my house. It happens at full throttle, 4500+ RPM and most commonly under load - like accelerating up a hill. It also seems to want to only do it on warm days. It was doing it last week when the weather was in the '80s and so far has not done it today in the low 50s.

Ideas?

Thanks,

Chris