That's been my experience. 13,200 is pretty much the average for mine. When I get over 13,300 the rpm reading bounces around all over the place.
Different max rpm for OE and NE 346's. I ran mine stock, ported NE or OE right at 13.8K sweet spot for my liking.
Has anyone here tried one of the Dixon / Strandix analog wireless tachometers? They're not so easily pocketable (too big) and probably more fragile than a digital tach, but the thought of a needle moving across a scale instead of jumpy numeric display is appealing to me.