I have a 92 cx hatchback with a jdm 1.5. The car is smoking REALLY bad when i get on it from about 3k to redline. Kinda a grayish black smoke. Ive heard several reasons why this is happening...valve seals, head gasket, piston rings. It is also using a little bit of oil. Any ideas where i should start or anyway to determine what needs to be replace without removing anything?