I chased vacuum leaks for several weeks on my 99. Culprit was brake booster line connector as well as J-pipe going to throttle body. Spec for my 99 MAF is 15 kg/h +/- 1.25, but forget that: like san rensho said look at the fuel trim in real-time. Plus the pre-cat O2 sensors should be fluctuating between .07 and .79, according to the manual. Post-cat are static as you noted.
Once I fixed the vacuum leaks it was still not right, so I replaced the generic O2 sensors and the MAF sensor, one at a time, with Bosch and that took care of the rest of the problem.
|