Hi, I'm new to the site but was wondering if anyone could help with a problem I have with my GB270. Sorry for a bit of a saga, but hopefully it provides most details needed for help.... Impreza GB270 2007, secondary air injection system turned off in ECU. Recently ran fuel lower than normal then had to put in small amount of 95 RON. Ran for about 70 miles very gently then topped up with Shell V-Power. After another tank of V-Power, got some hesitation when cold which quickly turned to mis-fire all the time. Have only had a fault code once (mis-fire cylinder 4) which was cleared and has not re-appeared after driving 7 miles whilst missing. (not using now, thankfully have spare 2000 Turbo ) Have tried new coil pack and plug in cylinder 4, no difference. Ran whilst coil pack off cylinder 4 and no noticeable difference, suggesting the problem is with cylinder 4. Does anyone have any ideas what could be checked next or advise best place to take car to in the Norfolk area. Any help would be much appreciated. Thanks