Mechanics - a few questions regarding carbon deposits
 

I am changing the knock sensors on my 1999 ES300 with 171K ( I have owned since 75k). I noticed the back of the intake valves on the front bank had a lot of carbon deposits. Should I attempt to clean them off or just run seafoam through several tanks of gas? (I am concerned about the deposits getting into the combustion chamber and causing damage) I also noticed evidence of the front bank head gasket leaking into the valley pan. I believe it to be older because the staining is pink and I changed to the universal antifreeze (green) a few years ago plus I am not loosing coolant. Could the 2 be related or just a coincidence? I do not really want to change the head gasket but I am feeling the "while I am at it" pressure building. I appreciate your thoughts.