It is def the psiton rings. If it doesn't smoke immediatly when you start it up, then it wouldn't be your valve seals. My car smoke from about 6,000 to 9,000 when I stomp it. And I know it is my rungs. My suggestion is that if youare going to change the piston rings, Just bore out and get new rods and psitons as well, might as well do it, while you got everything out. Also, replace every single gasket you can while you have everything out. It will save you a bunch of problems down the road, and it is cheap too.