The plug seems ok from what I can tell, but I'm not sure there's a great way to know 100% without doing some serious tear-down. I need to read through my FSM and see if anything in the troubleshooting section covers misfires. I should probably pull the plugs and check their screw caps too, they're nearly new IK-22's but I've been burned by loosening screw tops before.

The injectors are 318cc ones from the URD fuel kit, installed in 2006. So not exactly new, but not ancient... I might try some Seafoam through the tank though nice reminder.