Changed the sensor a couple weeks ago, fresh plugs- idles smoother than it has in over a year, and my highway MPG when zero the DIS at 60mph is back to 28-29 from the 24-25 it was pre plugs'n sensor, of course the new o2 probably had a lot to do with that...now, resealing the intake manifolds, upper and lower, the plenum started to leak coolant and the lower was leaking oil pretty good at the bell housing end.