hey. happened again today, but after the fifth or sixth time i reved it to 6 grand and a load of black smoke came out the exhaust. it smelt of petrol fumes quite bad and engine sounded bit 'burbly'. after about 20 seconds it was fine. i have just had the cat put back on for m.o.t, u rekon there might be a slight blockage through the exhaust system or something?