I had the same symptoms as you on my Coupe GT years ago, although mine had the 5 pot JS engine. I changed the oil to 20w50 and it seems to be a lot better. After 5,000 miles it would tap after giving it some beans but changing the oil would ensure it wouldn’t tap until the next interval. I did 108,000 miles using this method and didn’t miss a beat with regular oil changes.
To be honest, mikes2 will be more knowledgeable than myself, just thought I’d reply as I’ve had a similar issue in the past
