Try loosening the exhaust pipe at the flange where it meets the manifold by about 1/2" or so. I's possible you've got some sort of restriction on the exhaust system that's preventing the engine from accelerating. That's a remote chance, but long-idle vehicles have been known to accumulate all sorts of debris in the exhaust system thanks to mice and other critters nesting in the tailpipe.
Jerry

"It is better to be silent and be thought a fool than to speak and eliminate all doubt!" - Abraham Lincoln
Cringe and wail in fear, Eloi- - - - -we Morlocks are on the hunt!
There is nothing noble in being superior to your fellow man; true nobility is being superior to your former self. - Ernest Hemingway
Love your enemies and drive 'em nuts!