im in the middle of doing mine mate. Basicly mine was pushing oil through the rocker cover breathers, and it started sounding like a subaru slightly, wasnt missfiring but it didnt sound right, however it was still drivable. Do a compression test and see what comes up, I've taken my engine out today and im going to be doing the re-build shortly. if it is deffo the piston rings, Dont start the car up or anything just incase you damage something even more. Mine didnt smoke through the exhaust either