I took my bike for new tyre at muldoons in kirkintilloch.. They've been into bikes for years racing side cars at the TT and all.. I mentioned that the fazer was a bit boggy in the midrange, The old guy pull out some Forte fuel additive and poured the whole bottle into the tank I'd just filled the tank up. he said it was more than was recommended but he also said that as my pbike hadn't done much work in it's life and probably had spent a lot of time sitting in a garage, ( it only had 5800 mile on it when i got it.) that the carbs get slowly gummed up, mainly due to the additives in petrol nowadays. anyway suffice to say the bike has been through three tanks of petrol since and is no longer sluggish in the midrange. It also ticks over better and goes like stink. I've also fitted a K&N. but didn't notice any difference except a slightly different engine note..