Took my 1992 Ford Explorer XLT (4-door, auto 4WD, auto tran, 4.0 V6) for smog test (California) and it failed. It seemed to run fine, and indeed everything passed EXCEPT "NO (PPM)" -- Max 699, measured 2342! So, it's a "GROSS POLLUTER." (I now suspect this was caused by an unoticed missing 8"...