High REVS in Port-Fuel-Injection

Hello, I have a 1986 Oldsmobile Delta88, 3.8L, V6, port fuel injection.
I posted earlier that my fuel economy has gone down very noticeably.
One thing is that i notice that the revs are really high.
Sometimes specially when it was just started it will run at 30-mph, even with my foot off the gas.
What would cause a Port Fuel Injected engine to run too high rev, specially at start up?
This things can not be adjusted in this cars. So what could cause it?
Thanks!
Myc1972
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Here is some more info. When i accelarate i hear a kind of whistle and it goes away when i let off the pedal. Might be related?
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