Try a better grade gas or even premium for the next tank or two. Driving with misfires or pinging can be extremely bad on the pistons as it creates a great deal of heat. You may have simply gotten a bad tank of gas. Yeah, they say platinum plugs will last 100k but I started changing mine every 20K or so. Some of the '00/01 VXes do not like the Plus4s and will throw a code.