Hi FROSTYBALLS and thank You for the reply as well. Unfortunately I spend too much money for the car already. As I sad I service it (engine oil, Oil Filter, Air Filter, Cabin Filter, Fuel Filter, Spark Plugs, Front Brake Discs, Front Brake Pads, Rear Brake Pads, Rear Brake Caliper, All three Wiper Blades) and I also bought 2 new tyres with a wheel alignment, as I'm doing that with all of the cars I'm buying, because I can't rely on a dealers statement that the car was just serviced, as they all saying that. This one even has a receipt that is serviced around 5000 miles ago from Toyota dealer, but when I did the service it turns out that the Air and Cabin Filters where not changed the last time (whenever that was). So when I add the sensors the total amount I spend for all repairs is around £900 and I think that even if I return the car to the dealer there is no chance to get those money back and as I can see in ebay a new engine (second hand) will cost me around £300. So I'm thinking to try the ideas that TonyHSD gave me and try those additives and if they don't work as well I will change the engine and hopefully that will be the end of the story. The thing that most makes me angry is that I thought that Toyota is one of the most reliable make for cars, but may be I'm just unlucky. I also have some warranty which I might use to try and repair the engine. I will post the results as soon as I have some.