I often see these listed on ebay for £400, but then again who has had CATS fail?
I keep mine in a box in the garage ready for when I revert to standard to trade/sell the car. You can then sell the aftermarket downpipes for a reasonable ammount.
Equally important to have as a backup if you fall foul of the more stringent MOT rules.
My advice would be to keep hold of em - £100 is nothing!
2008 E90 335i LCI M Sport / Manual / Black / Red Leather / Avon ZZ5 / VMR710
Mods: JB4 G5 ISO / BMS Back End Flash / BMS DCI / AR Design DPs / ETS FMIC / Meth Injection / Spec Stage 2+ Clutch / BMS OCC / Cool Carbon Brake Pads / RB PCV Valve / Forge DVs / M3 Control Arms / Bilstein B4s / Eibach Pro Springs / Eisenmann Race
Wish List: LSD