Just some worthless info.
Action Plus is same hight tall as the RPM (not air gap).
Has,same size ports in width as the RPM. But RPM has,1/4 " large ports in hight than the Action Plus.
Personally think the Action Plus and it's smaller ports would be better low end tourqe on smaller cam street 340_360. When i say smaller I meen street, not street strip. To bad Ma no longer makes the DP M1