Putting Vpower in wont make any difference to the engine rattle, what a load of pi$h they are telling you. The rattle is due to the timing chain tensioner not keeping the chain in the right tension. Petrol goes into the cylinders not into the timing chain area.
Go back to them and tell them you want the latest fix of PUMA number 10686850, I think they are on number 16 or so now.