Doesn't need the lead for lube. That's what your stroker oil is for.

Are you looking for a lubrication increase and octane increase or....?

50/50 avgas/ULG will increase octane and also slow the burn, but you could lose power, not gain power, by increasing the fuel octane.

If the engine is setup (compression, ignition etc) to run let's say 91 octane fuel then you will lose power by throwing in avgas.

There's lots of variable. You need to use the fuel your engine needs, not necessarily what the guys at the track are using.

If you want to increase the octane of a pump fuel then you can add an aromatic such as toluene or xylene, but they're expensive and to be honest the fuel companies blend in such a large percentage of aromatics these days that it doesn't make too much difference.

If the bike runs well now with whatever fuel you're running then leave it as it is. Or you'll end up chasing compression ratios and ignition settings to get the best from it.