I don't know about the helicoiled rocker assemblies (I'll ask my mechanic the next time I see him, which coincidentally is really soon to have the bolts re-torqued). Would the bad rockers cause this problem?

Motor mounts are brand new though (and the bracket which holds the drivers side one to the engine). The idle that I feel in the chasis seems like its vibrating only in the A pillar on the driver's side.

There are a lot of questions floating around in my mind about this, like if its possible the O2 sensor is at fault or the coil is at fault (although every mechanic I've talked to says its not possible), or if its maybe the ECU acting up.

Sorry for leaving some of the other maintenance out of the original post.

Side note, I just calculate my mpg and it seems I'm getting around 21 for highway driving (75mph around 3krpm). Is it possible I'm running overly rich?

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87 300E
202k on the clock