I have the same problem with my janome 6600. I took it in to the dealer and the guy said I was not stepping on the pedal correctly.
I have only been sewing for 50 years or so. It is a little hard to believe that I have not been stepping on the pedal correctly all this time. I will have to check out the lint thing. You may find this hard to believe but I have found that if you turn it upside down and step on the button instead of using it the correct way it does better. Also have any of you noticed on what I am calling the button on the bottom there are grooves wearing in the side?