To anyone thinking of going down the BoosterPlug route....read on.
I watched AndyManCam's YouTube video where he installed one on his FZ1 and thought I'd try and find one for the FZ6. Well, it turns out that they are £129 a go brand new.....but the internal gubbins on all models appears to be the same. Just the plugs at the ends are different for each motorcycle model.
So, my solution isn't quite plug'n'play but very close.
I picked up a BoosterPlug off Marketplace for £60 and then grabbed some no-strip wire connectors off Amazon for £8
https://www.amazon.co.uk/gp/product/B07DK7HBKRIt is as simple as it sounds - cut the female plug off the BoosterPlug (with a good 8cm of wire attached) and attach a connector at each cut end. Cut the female plug off the AIT sensor and swap 'em over whilst keeping the wire colours in the right orientation.
Works a treat! Much smoother acceleration and less jerkiness when opening up the throttle from idle in 2nd gear.
Still got half a tank of fuel so I'll fill up at some point and log the mileage for that full tank on Fuelly and see if mpg changes. By all accounts it doesn't change at all, but I'll find out for myself.