I've been trying to eliminate any potential causes of pinging so I changed back to the plugs that allegedly were original equipment but it barely runs, backfires, and has no power. Does anyone have any insight into this? I've asked multiple people over the last twenty five years, trying to get some insight and no one has any answers.

My vehicle is a 1989 GMC C1500 5.7l. The plugs that every cross reference tells me are original equipment are CR43TS. They do not work for my application. I spent two years trying to figure this out twenty years ago and found out by dumb luck that the problem is those plugs. Although everything I read tells me it's not the plugs. It runs just fine on R43TS and R44TS plugs but I was trying to eliminate potential causes of pinging.

The only difference I know of is that the "C" in the recommended plugs stands for commercial. That tells me nothing. I can visually see that the electrode is larger on the commercial plug but most people swear by them on these trucks.

Any insight is welcomed.