No mufflers, just added the headers. Modular valve, power brake booster and vacuum advance to distributor all disconnected and plugged as are all of the vacuum ports on the carb. I'm using 2 box fans on the radiator too.Do you have mufflers?
You say "all the vacuum lines are plugged except the pcv." What about vacuum advance to your distributor?
When I started my car for the first time I had a couple fans blowing at the front of the car. Mostly to encourage fumes and exhaust to go out my garage door.