I am running a new 427 Small block with a cam spec of 233/239 @.05 and .544/.55 lift. I ran a 650 Edlebrock performer carb for a while without any problems. I did have to drill the primary butterfly valves. In order to maintain about 10" vacuum I have to set the idle on both at about 1000 rpm. When I put into drive it drops to about 800. The holly seems to want to foul the first four plugs only (1,3,4 & 2) the rear four remain normal. Because the primary valves favor the first 4 cylinders, (dual plane) could I have them set to rich? My theory is air/fuel from the secondary is flowing through the fuel being drawn from the primary idle circut creating a rich mixture. When one of the rear 4 cylinders draw, they are pulling air/fuel from the secondaries but most of the fuel rich mixture from the primaries is falling out. Any tips?