MDMA making your mouth slightly numb?

I recently came across someone with a large rock of MDMA. It is kind of a clear-ish / off-white / brown color. It has passed Mecke (Very fast dark purple to black), Simon's (light to dark blue quickly), and Marquis (kind of clearish to dark black fast) tests.

All three reagent reactions produced smoke and fizzled indicating that it's great stuff, but the kicker is... it makes my mouth and tongue slightly numb when I taste it. Nothing like cocaine, but theres definitely something in it causing numbness.

I've read that some people have cut MDMA with procaine before, which I guess could explain the numbness, but this is my first time actually experiencing this with MDMA. I am still going to give it the Pepsi Challenge this weekend, but has anyone else come across molly that numbed their mouth?