Stickbuilder

My 93 300e 2.8 had started backfiring through the intake when rolling the throttle on (under load) when warm. I looked for vacuum leaks and such, but finally decided to change the plugs. I believe that the plugs were original or nearly so. The gap had eroded to somewhere in the 0.050" range. Lucky it still ran at all. New plugs gapped to 0.032" and test drove it. Smooth as silk. Plug color looked great on the old ones. Hoping for the best. Can't really understand why they had been in the engine for so long. P.O. had all other maintenance performed when scheduled and the car got a new wiring harness and head gasket several years (but not many miles) ago. Maybe they put in the new plugs then. Does not show them on the repair order though. Who knows?