I've got an avanti head on my TS1. It seems to run very cool. I've just repositioned the thermocouple so it will be next spring before I have good data though.
One thing to bear in mind is that they limit exhaust choice. Jl3 curly had to be belted with a club hammer slightly to fit, not much but mine was scruffy so I didn't care. Bgm clubman wouldn't go near. Af 48mm clubman wouldn't go near either. Avanti ex box fits nice though.
One more thing is that when I look at the bgm head, it's 'only' 125. Maybe it automatically calculates discount? But don't think I get that much, more like 10%