I performed a cylinder pressure check the other day on my 240Z. I'm concerned about the results. The first two cylinders were 140 psi. Three and four ranged about 125 to 135 psi. The last two ranged about 130 to 135 psi. What is the normal cylinder pressure for the L24's with twin SU's? The car runs fine but starts to smoke when idoling for a long period. Could the valve seals be leaking????