Yellowing Problem
 

The plastic strip where the top sets to the body has turned yellow in spots. Wondering if anyone else has seen this problem ?

I have not, but if your Z is in the sun a lot the UV could cause yellowing of the clear plastic. I'd hope Nissan would use something that's UV resistant. If your Z is still under warranty you should definitely have them replace it. Better yet, if it were me I would get some better quality adhesive-backed plastic and replace it myself.