I removed the lower intake the other day to replace the knock sensor, and while examining the cylinders in the head today, I noticed that one of the pistons is sitting noticeably lower than all the rest. It is the middle one on the right side of the engine. Cylinder 5 I think. I'm just guessing that these are the pistons and cylinders so correct me if I'm wrong. It is located directly beneath the lower intake manifold. Any ideas why it would be sitting lower than the rest?

 

You're not looking at the pistons if you only removed the intake manifold. You'd have to remove the cylinder heads to get to the pistons.

Pics help.