This is a picture of Nissa VQ35 engine from a 2005 Maxima. It is a picture of the intake port, and what you are looking at is caked on catalyst on the intake port. What happens many time with these Nissan engines is that the catalyst breaks down and gets digested back into the engine (the catalst dust is caking on in the intake port) and then the cylinder walls get washed out and then you have little/no compressions and thats the end of the engine.