As soon as I turn the engine on I hear knocking.then after it idles and reaches normal running temp it starts to smoke behind the end of the down pipe.I look underneath and still can't tell where and why its smoking.I do see some smoke coming from the catalytic converter.Haven't seen any traces of antifreeze in the oil but smell gas in the oil on the dipstick.can my turbo be going out the door cause when I drive it,it has now power or pickup.