Well, since I hit the 100k club thought I might as well change the plugs. My MPG had went down a little and I was starting to notice a little bit of a miss when starting cold. It was a pretty involved situation. I had to remove the upper intake off (per GM instruction) to get to the back 3. If any of you plan to do this, make sure to take off all the insulation first from the intake. I thought I could cheat it but it just fought. Took me about 2 hours to do (changed oil at the same time). Only thing that concerned me was all the oil in the intake tube. 2 this summer when driving hard on long trips I noticed it using a little oil. I now know where this oil has been going.