I run that intake with the thin paper gasket. no issues, I don't have the heater either. have run it ( just to move around the driveway ) during winter without issues.
had a 450 on mine, was never able to get the tune right for me ( mechanical secondary's didn't help ) have since switched to a FiTech setup with good results.
The Quickfuel Slayer 450 CFM has greater adjustments than many other carbs. The vaccum secondaries have adjustable options to open up at various throttle percentages.