[A26B]

Originally Posted by Lowflight

Could the plug-gap have anything to do with it?

Not in my opinion. Under the worst scenario, you would experience a miss-fire, specifically incomplete combustion or no combustion at all, i.e. a dead miss.

I have yet to see or hear a plausible explaination regarding the gap difference between the early & late LT5. All, use the same ignition system. Plugs are interchangable, both washer & tapered seat. IMO, 0.050 gap is correct for the Iridium plugs. At the risk of being flamed, I would recommend running 0.050 gap on all years just for the benefit of a bigger spark. If the rest of the ignition system is in top condition, it should perform fine.

DTC 43 is the knock sensor. The service manual procedure for checking the knock sensor loop is fine if the sensor has completely failed. Mine failed intermittently. Resistance checked fine several times until it was finally open the last time. A real bear to analyze under those conditions.
Good luck with your diagnostic procedures.

If you're planning on calling Marc, please post his opinion. Always interested in Marc's wisdom!