I didn't like the air gap on my 454. It was slow to warm up and things always seem to fall into the "air gap" area under the carb.
Had slow warms up issues if temps dropped below 55 or 60F. The carb would stumble right off idle for 15 to 20 minutes, until the carb got warm enough to run right. I could richen up the carb to over come the stumble issue when cold but then would run very rich once the carb and intake warmed up.
I ended up selling the air gap to a guy on this site and fully disclosed my issue with the intake. I now use a regular style intake with restrictors in the exhaust cross over ports. much happier now. Carbs need heat to vaporize the fuel properly.
I say, get a regular RPM intake and forget the air gap.