Strange engine question?

Ran my sb stroker today chasing a oil leak , had to pull a header to see the back of a valve cover for leakage , found oil soaking around #7 header tube @ the head , did not see anything so I cleaned up the oil & ran the engine at idle without the header for a short time to find the leak , well this puppy idled @ 2200 norm is 1250 ? whats up with this ? tried to back off the idle screw till it ran out & was still at 2000 .Found a bad valve seal on #7 & its pumping oil out the exhaust port that was the leak but whats up with the rpm , we run short tube 1 3/4 fenderwell headers open with 3 1/2 collector can they be too small?

It wouldnt be the header, that size is normal. Do
you have a choke or a choke cam, look to see where
the throttle blade is(is it open too far)

sounds like you have a valve guide that is toast too.

I can't help on the oil leak but, running the engine with no
header on it is probably what caused the high idle. During
camshaft overlap, the piston is sucking fresh air into the
cylinders, through the exhaust port, leaning out the mixture.
Just like leaving a vacuum port open on the carburetor. It's
also a good way to warp the exhaust valves.

Its definetly not carb related , the exhaust sucking fresh air sounds about right ,its running like it has a huge vacume leak , I put the header back on and Idle went down , the cams cut on 106 with 50 odd degrees of overlap , the guide feels tight as far as the wobble test goes but ill probaly pull the heads they have a good amount of time on them ,