My mixture is a little on the rich side.. but that is how Bennett built the motor. I have also noticed that I get a little bit of popping out of the pipes. I wonder if your plugs could be a little fouled up? The only other thing I can think to check is the plug wires and connection. I had a bad plug wire on #1 cylinder caused it to run real rough. Never would have thought brand new plug wires from Ford Racing would be bad with less than 500 miles on the car last year. It is always the things you least expect. But that's why we love these things..
J.A.