When you find out where your contact purchased the Pirelli tires, please spread the information. I have always liked the Pirelli Diablo series for the bigger bikes.Pirelli has a nice looking tire for the Grom. I was leaning towards the Michelin myself, then another member (AJ510 I think is his forum name) on here pointed out a good point while at our last (my first) track day. The Michelin's have a lot of siping, or pattern, on the edge of the tire. The Pirelli's are almost slick like on the edge.
I haven't tried the Pirelli myself. One of the regular local track guys bought some for his Grom, but he wasn't able to make the last track day, so I wasn't able to hear any feedback. Looks like a great tire though.