fill your tank up to around 3/4 doesnt have to be brimming out of the top. Get some stuff from forte... it is proven and we use it at work to bring the emmisions down for MOT Test on diesels quite alot..
use FORTE gas treatment, pour the lot in your tank, and also along with that use FORTE Specialist injector treatment. the gas treatment vapourises and cleans alot of internal parts. wont to any harm at all.
the only things i wouldnt use to be honest is an engine flush as it holds all the stuff in suspension oil, grime, carbon build up etc. just dont fancy it striping everything of oil or dislodging something and it clogging an oil gallery. if you car has been serviced with regular good oil changes then that should be fine. so dont be tempted by the engine flushes.