I would check the pump timing as could produce quite a noisy engine if way out of time. Pretty easy once you follow instructions either on this site or from a service manual. Sady has adjusted pump timimg more than once I believe. Just a thought if perhaps the last guy got the pump too far advanced or changed it with the same results. Would answer why the engine quiets a lot when you pick up some rpms. Also not the best ideal to run the engine for extended periods if pump is a long way advanced. Possibly the bearings in the turbo have rusted with twelve years of sitting around but they can be replaced at home i understand. Again threads in archives a guide to how and locating economical bearing and seal suppliers. The best with your new car. Just an abstract thought someone more knowledgeable might care to comment on. I assume these pumps have a mechanical advance system. If it is stuck in a pump what are the symptoms? I would think simular to his but probably wrong but that may be why the pump needed changed in the first place although unusual I would think. I just do not know enough about these cars.