[vbdig]

I had a similar response when I increased jet size. I am at 3500 ft altitude, and went clear down to a 68 on primary, and a 67 on secondary. Also a 4.5 power valve. It ran pretty good but the Holley tech people said something must be wrong with the carb to need jets that small. I sent it to them and they said nothing wrong. I think either my msd is faulty or this engine needs far less fuel than everyone says. By the way, my plugs were gapped at 45 from ford racing, I have tried increasing gap to 55 with no improvement.