u/Clear_Attitude5206

Hey guys, new here, but not to engines.

Built a 1.8t with 400hp. Runs great, built and tuned well.

Recently due to gas prices I put in lower octane and noticed it not going over 260 km/h (Germany).

Slowed it down a bit drove home. Couple days later it hat this issue where the spark would cut sporadically.

Now I took out the spark plugs and found one in pretty bad shape. All the other ones look great. Also the corresponding cylinder has scoring.

Is the scoring dramatic or could I still run it like this, after finding the reason for the damaged spark plug?

Two last images are healthy spark plug and cylinder wall.