Filters: Best place to get them is from BR Special Tuning.

http://www.motorcycle-exhausts.co.uk/Yamaha_DNA_Filters--category--785.html

Kev Mod/O2 Controller: Best price can be obtained from Kev directly by send him a PM. He does sell them on ebay, but they'll be a little more expensive to cover his ebay fees.

http://www.ebay.co.uk/itm/Yamaha-XT660X-XT660R-XT660Z-XTX-XTR-XTZ-O2-Controller-Fuel-Mod-/141627590325?pt=LH_DefaultDomain_15&hash=item20f9a 986b5

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