ok back on track. It may be your spark plug tube seals. If you get a burning smell after a good drive and some moderate smoke then that would probably be the culprit, but that may not always be the case. If it reaches the floor it most probably is the inner most plug which can definitely reach the floor without having hit the exhaust. To check remove the passenger wheel and the wheel liner. Easy to do this with the stock jack. here are some pics of what you'll see.
This one is quiet oily because the tube seals needed to be changed. Quite messy.
You will need to remove this wheel liner.
