I have a 1999 Grand Prix GT with 170,000 miles. I drove to a basketball game 2 blocks away and it was perfectly fine and normal. After the game I started it up and it was vibrating really bad and the check engine soon was flashing so I knew it was misfiring. So today I started it up to drive into the garage and it was normal again. I checked cylinder 1 and noticed the plug and wire have been replaced before. The rest of the plus are delco but this one is an autolight double platinum 606. Would different plus cause a sudden misfire? Looking forward to your help. Thanks. Here are some pics. Do you think the delco plugs are original from factory?