The engine is a BBC 598. Now one thing I'm unsure of is when you say down 10 jet sizes your refering to numerical values right (currently a 164 down to a 154). I've alway been running gas and each steps down in increments of one where alky seems to step in 4's. (FYI I started at 172 jets). I'll try the idle mixture screws but with the bypass loop on the enderly pump at an idle I only have 2.5- 3 psi but as soon as I touch the throttle it jumps to 8. Should I be looking at changing the jet/ pill in the pump to limit the amount of fuel up to the carb?