Usually when I hear "surge", I think of a lean a/f mix or too much advance.
You're correct in thinking that changing the primary jetting shouldn't affect the idle quality. Is there a chance the float level got changed during the work that was done?
If you find that the curb idle screw is far enough out to raise the idle speed that the carb is transitioning into the cruise circuit, you might want to hook the vacuum advance up to a manifold vacuum source (if not already).
This will raise the idle speed and then you can use the curb idle screw to lower the idle speed and by default lessen the transfer slot exposure.
Last edited by cobalt327; 05-24-2010 at 11:48 AM.