Some very fast guys run PVLS but the FASTEST run stock. THe Puerto Ricans all run stock ignition and have the record for fastest Twin Cylinder. I believe Dan Hull runs stock, or at least builds motors for customers with stock ignition. I've had 2 of his motors. My PVL on my 4 mil finallly took a crap, I think. Everything tests within range, but I won't know until I put stock back on.
IMO, the worse thing about the PVL (other than installation) is that it doesn't retard the timing as RPMS increase (unless you buy the $650 programmable PVL- jury's still out on that, I think.)