Agree with patrick in that it's a timing issue ( although I have never seen 30 degrees of mechanical advance in a distributor before ). It sounds as though you have too much timing coming in too soon ( curve is too fast at the bottom end ). You can try replacing the light spring with a heavier one, or to verify that's the case, set the initial timing @ tdc or even a little on the retard side and see if that perks up the low end. It will obviuosly kill the top end ( and the vacuum )but it's just a test to see if the initial curve is too fast. For your set up, I would run about 12 mechanical degrees in the distributor ( 24 degrees @ the crank ) with initial timing at 12 degrees for a total mechanical of 36 dgerees - Curve to start around 1200rpm and all in around 2800 rpm. I'd run about 14 degrees of vacuum advance. This would give you a total of 50 degrees at cruise - 2800 rpm or above. Very common set up for a streeter.