347,
I have to agree with Matt, it's not likely a cam problem. A flat spot under 3000 RPM is probably a too small idle jet. Try going up to a 55. Also, the idle bleed adjustment should be about 1 full turn open on all barrels when properly set up. Webers operate on the idle circuits up through approx. 2500 - 3000 rpms where they transition to the mains. Don't mess with the air correctors to cure the symptoms you've described. BTW, F11 tubes are fine. My 48mm IDFs are set up similar to yours. When I was setting mine up, I had some popping and flattness below 3000 and all it took to smooth it out was opening the idle bleed adjustments to 1 full turn. Good luck.
Mike
