1st Gear Member
Join Date: Jan 2004
Location: Central New Jersey
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the converters can be checked using a backpressure guage. it mounts in place of the pre-cat o2 sensor, you bring the rpms up to 2500, anything more than 1.5 psi indicates a plugged converter.
as far as the multiple misfire codes I would check,
1) the spark plug connectors, make sure they aren't sitting in an oil bath.
2) the pcv plate in the back of the intake.
3) the manifold gaskets for vacuum leaks.