I've never tested a RPM air gap against a decent single plane but I have tested a BB with a Eddy Torker 2 against the Eddy RPM and again against a Mopar M1 single plane. The Torker 2 was the worst,20 to 30 HP behind both of the other two intakes from 2500RPM up to 7000 RPM, the RPM intake made more HP and torque below 5500 RPM than the M1 did but the M1 intake made more HP and torque above 5500 RPM work shruggy
That was with the same carb and no jetting or timing changes within 4 hours of all three test wrench
I ended up putting the RPM back on the motor after discussing those dyno results with the customer, he ended up liking that combination a lot up
IHTHs

Mr.Cab Racing and winning with Mopars since 1964. (Old F--t, Huh)