[Squarebod]

I have been driving without it hooked up drives great at wide open a little slow on the take off and I get a pretty good jerk late like my secondarys are opening up a little late (could be a fuel issue I'm running a stock pump but seems to do alright with keeping fuel in the bowls in the driveway my friend has one on his 383 does fine). I have a stock HEI laying around that came off it originally I could try. Got a full assortment of jets, pump cams, and secondary springs to play with my carb but want to get my timing dialed in first. I'll be back to it tomorrow spent most the day replacing the heater core that filled my ducts up with antifreeze was quite the mess but got to clean,seal and repair it right. Would the low manifold vacuum affect the vac advance? Or vacuum secondarys? I know it had a dramatic affect on my brakes.