Went back to tuning with the os #8 instead of the stock hpi cold plug, got SLIGHTLY better performance but still can hear it being limited in upper rpm.
I hope it's just not just the way this engine is. I know it's not a race mill, but the 2.5 in my rustler screams compared to this thing, by sound.

Seems to have adequate pinch & running vp 20% master basher

Edit: going to try a traxxas long reach plug to up the compression just to see, calculations shows enough clearance not to worry