it's an art isn't it? Have you tried to come off at idle and waffle it? Sometimes converts like to flash instead of loading them up. My next question is why is your vacuum so low? Can you adjust on the carb to get more? I guess you could get a adjustable P-Valve and crank up the pressure? I used a Mopar 175k behind a mild 440. It worked best when I held it at 1200 and stomped it on the last yellow, it would flash to around 2800 and take off. 1.68 60 foot.