Recently i got a high mileage sc300 and it has been producing lots of white smoke from the exhaust, as well as a strong smell of gas. I've searched around and saw lots of people with similar symptoms due to a bad ecu. Should I check out the ecu first or check my spark plugs (which were just replaced) for signs of any leaks or other clues?

 

If you have not had the ecu refurbished it’s a good place to start. Known issue and lots of discussion on this in other threads. I think you will find similar symptoms as yours in many discussions, but I guess there are other things that can cause it.