RZR 170 DynaTek/Race fuel/ Plugs

Hi both my kids have 170s... both have sparks racing exhaust and Dynatek EFI FS programmers.. clutches ect ect ect...

This weekend i had a drum of vp MR12 so i ran it in both, One ran great and one destroyed a plug, looks like it ran extremely hot. Question is what plugs should i be running? im guessing that switching to the MR12 fuel it ran much hotter.

thanks in advance