I took my top end apart to have a BBK installed and noticed that thru the intake port one valve was clean and the other was all carbon coated. Does this mean that that valve as not seating right? It had a standard valve (tune up) not to long ago! Its also not related to valve clearance, I check it often and it has never been out of spec. I put it back together because head work and valves are soon to come. I was just wondering if anyone has seen this before?

Normally they both get a little black over time.
I don't know why one side would stay clean... unless it is not flowing right.