Small Engines (Lawn Mowers, etc.): John Deere 445, john deere 445, breather cap

Question
I have John Deere 445 22hp OHV fuel injection Kaw which has only 115 hours on her.  After roughly 15 minutes of mowing, it starts to stall and puffs of black smoke comes out of the muffler.  I have changed the fuel pump, made sure the breather cap on the tank was clear and replaced the plugs.  The plugs seem to burn dark and dry.  Any suggestions would be greatly appreciated.


Answer
This a job you can't troubleshoot at home.  You are going to have to go to the dealer and let him run a computer diagnostic on the efi computer.  Parts are way to expensive to guess what's wrong.  You win the prize, you are the first of the 700 questions I've answered that I had to send the questioner to a dealer.
Sorry.