Mine used to rev and idle at 3k when i had the idle valve plugged in, if i unplugged it it sat perfect just under 1k. I thought it was the valve that was no good, but when my engine was rebuilt i was told it was caused by a gasket (cant remember which, sorry) not the idle valve.
(I had cleaned it too and it made no difference) Soon as the new gasket was on it was fine again