Hi all , thanks for your replies, I'm now convinced that at the very least I'll support; the $10 is very much worth it, thanks.
Secondly, Waynovetten, the "they" I'm referring to is because the last accident I had I was knocked unconscious and I never saw my XT660X ever again, all I saw was the boot of a paramedic whilst my head lay on the tarmac as he spoke to me. Of course, most accidents aren't that bad, but if I had another like that and hadn't told them about the mod...who knows, I'd rather not take the risk.
I have noticed, after fitting the Akra cans, that the exhaust smelled "hot" they weren't hot it was just a smell of an engine running very warm, so that info about the fuel ratio, and Yamaha running it slightly lean rings a bell, hence my reticence to filter even more.
I actually enjoy the bike such as it is, but everything can be improved..
Still, as has been said, this forum is easily worth supporting, you've all been so helpful.
Jules