'95 Eldorado engine surge

This is an enquiry for my father-in-law who has owned the car since new.
1995 Cadillac ElDorado engine surge
While driving, the auto will begin to accelerate without the gas pedal being
depressed. With
foot removed from the gas pedal the auto will continue to accelerate and go faster and
faster until the brakes are applied. After the acceleration/breaking cycle has occurred once
or twice the automobile will then function normally for the remainder of the trip.
A local mechanic has attempted to solve the problem by clamping off an air-line which has
solved the problem somewhat but now the engine idles at a (slightly) higher RPM than
Any ideas?
Thanks in advance.
From 30 feet away she looked like a lot of class. From 10 feet away she
looked like something made up to be seen from 30 feet away. Philip Marlowe
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