I know there's been many posting on idle issues, but after all the searches I can't figure out my problem. My car starts, but initial idle is very rough and is less than 700 rpm. One thing I found strange is when I hit the gas pedal nothing happens, but on the second blip of the pedal the engine revs as expected. After a couple minutes of running or a drive down the block everything seems normal and the engine idles at 1000 rpm for the rest of the drive.

Here some specifics:

1) Raby 9590 cam and valve train with swivel feet and steel pushrods. Just verified all the valves are adjusted so the swivel feet turn easily for 0 lash.
Should I set in ~.002 of clearance? Read some postings saying initial warm-up of valves causes tight tappet clearance until engine expands.

2) Fuel pressure at 31 psi. Increased from 28 psi (I know a bit low) and seemed to improve a bit at 31psi.

3) About 300 miles on new rebuild.

4) AAR verified working. Just bought one from 914ltd.

5) Tested with AAR hose to atmosphere and engine revs to about 2100 rpm on cold start-up. Tested with AAR hose on broken AAR adjusted to full open without improvement.

Thought I'd ask before trying to build a custom AAR valve to adjust for more air.

Could this be a compression issue? I haven't run any test but I'm hoping not.