Dishwasher running smells like rotten eggs

Two yr old Kitchenaid D/W problem started about this summer and progressively worse with smell of rotten eggs, sulphur smell when D/W is running you can smell it coming from vent in D/W and around D/W and when it drains into disposal. First I tried totally cleaning disposal which we rarely use with lemons, baking soda, a bit of bleach. Smell also seems to emit from tube that D/W connects into disposal, so I tried cleaning the stainless tub of d/w with everything including bleach finally called service and for $100 he cleaned out from underneath housing in bottom of D/W, grease/soap scum. Problem was rectified for about a week then it came back. And I was very careful not to put too much deteregent,always run hot water before putting d/w on, but smell which was gone for about a week retuned... Needless to say I called back service he looked to see if there was more scum and it was clean... The smell is so bad that I cannot be in kitchen when it is running. I have even tried a d/w cleaner and ran that through, also I always use hi-temp scrub hoping the hot water will get rid of smell, I basically wash my dishes before I put in they do not sit in for a long time. I am at my wits end. Told my husband I want a new d/w..last d/w was a 25 yr old plus Hobart never had this problem. Is there anyone who could advise? The next service call, he said he will put a new tube connection from d/w to disposal.