i have an edelbrock 600cfm performer carb with elec choke. i have the idle set at 900rpms in park. my problem is that when you rev it up to 2000 or higher the idle dosn't go all the way down. it stays at about 1200-1500. the throttle body goes all the way back and hits the idle screw but it stays at a high idle. you have to tap the gas to get it to go down. i don't think its a vacume leak, i just changed the intake and made sure everything was sealed good and it did it before too. any ideas?

 

did you check to see if the secondaries are sticking open at all?
the return/activation mechanism for the secondaries may be hanging up.

 

my car was doing this too last summer. i found out that the throttle was not fully closing, the problem was the tension in the return spring. i can close it by hand so the idle go back low...

check this out... get the hood open and remove the air cleaner cover, rev your car and slowly release it... then it should have stayed at your 1200-1500 rpm like you say. goto the carb and use your hand to close it, if it work get a stiffer spring.

 

i found the spring was stretched out so i compressed it and heated it up to get it back to where it was. it seams that there wasn't enough tension, it would hit the idle screw but if you pushed it it would go down, now it is working better.