Get the filters from BR Special Tuning:

Filter Stage 1
Air Box Top Cover Stage 2
Air Box Side Cover Stage 3

For the O2 controller and Kev Mod either contact Kev directly by PM, or use this ebay link...

http://www.ebay.co.uk/itm/Yamaha-XT660X-XT660R-XT660Z-XTX-XTR-XTZ-O2-Controller-Fuel-Mod-/141151057905?pt=AU_Motorcycle_Parts_Accessories&ha sh=item20dd4237f1

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