Rpm stuck at 1200. Any ideas ?

[gschretter]

Back Ground Information:
Chevy 350 pre-vortec head.
Holley Off-Roard Avenger 750 cfm carb. - 10 months old
Headers - 3 months old
Normal gas.

New Holley avenger intake put in about two weeks ago.
Had the gas tank cleaned and put on new fuel filters.

Starts great. Just touch the key and it starts.
Has lots of power.

The idle screw has been removed since I can idle so low with no problems.

What Happened:
I drove about 20 miles on a warm day.
Gunned it once getting onto the highway.
When I took my exit and put in the clutch the idle stayed at 1200 rpm
Normal idle rpm is 450.

The choke works fine because the high idle kicks in and idles at 2000 rpm but when I hit the gas the choke turns off. So no problem there

Have not been off-roading in the vehicle in over two months

Any ideas ?

Timing is fine / Air - Fuel seems fine.

Thanks in advance for any help.

[gschretter]

I sprayed B-12 did not do anything.

I removed one of the vaccum hoses and started it.

Fired right up and idle normal.

Cap the vaccum hose up and the problem was fixed.

Why would removing a vaccum hose and starting the car fix the high idle problem ? Or was it the B-12 finally fixed it.

One thing I thought was weird is when I crimped the fuel line and when the fuel was getting low in the carb the idle got really high.

One of the fuel filters was really dirty even thought I replace it a week ago.

I guess some kind of high pressure fuel problem caused by dirty fuel filter ? Does that make sense.