slight miss

i have a thermoquad on a 408 stroker, engine runs awsome over 2000rpm, no dead spots, bogs spits ect. but when i try to idle along under 2000rpm i get a slight ''miss''. i have played with initial timing and air screws with no luck. what would be the next step? thanks in advance.

I've got the same issue with a stock 273 2 brl. Feels like a fish bite in the pull along the road. Nothing I've tried made a difference either.