my beza just broke down, givin it some beans down the a17 and all felt a judder in boost then lost all power, car does start revs are all over the place, but just konks out, rev the engine and a throaty nosie from the back of the engine thats what it sounds like its cumin from, backfirin lots no engine light on or anythin recovery man said my cat was fu**ed but i think it is a gasket gone some where any help would be appreciated asap how much to fix if you now what it is?????