Port my current M1 single plane or install the RPM Air Gap?

That’s a list of the who’s who.

Leave some links?

Personally I’d run with Ratbastards suggestion.

Your exhaust is TTI W/an X pipe?
This throws away low end torque. A pressure wave cancellation box should have been tested after the header for increased low end torque output.

Questions!!!!

What size tires are you running?
What is your overdrive gear?
What are your cruise RPM’s?
What model carb? (Mechanical or vacuum?)

At 422 cubes, getting a tic over 20 MPG‘S is very very good.
The 2.196 final drive ratio with the cubes and cam size, WOW!
The X pipe is from Dr Gas the rest is TTI. I ordered a cam and RHS cast iron X heads for the 408 in my truck from Brian at IMM and I asked if he had tested X pipes as I like the sound and wanted them on everything no matter how difficult they are to plumb correctly. I had mentioned my Dusters exhaust telling him I was considering stepping it up to 3" at the exit of the X and 3" all the way out and installing that X on my truck. Brian said there was power to be kept by not going 3" and leaving it as is on my car and getting new for the truck. Was he saving me work or keeping me from making the car worse IDK?