assam

Hey all some of you may be aware I have a boosting problem where the car jerks violently at higher revs when giving it some beans and thanks to all who have replied to my problems with advise...im a total newbie to the whole subaru world and a wonderful world it is!!! and im not the sharpest tool in the box when it comes to technical stuff and repairing/checking things myself!!
Does anyone know of a specialist or any garages I can take it to in or around London????

Please advise

Cheers