A man is "porned out" when he has watched so much porn, he loses touch with reality. Typically he over-manscapes, with the misguided impression that it makes his dick look bigger, and insists on trying painful positions he has seen in skinflicks. Usually thinks he's amazing in bed, but has no idea of what a woman wants.
"I really liked him until we got busy. What a disappointment, he's totally porned out. (sigh)"
"He really porned-out his junk, so he looked like a hairless twelve year old. (shudder)"