When i drive my 05 Optima and run the AC on Max for about 15-20 minutes or more, when i start to shift, the clutch begins to squeak and get mushy. After a few minutes of this the clutch will eventually stick to the floor. I brought it to my local Kia dealer, which was a mistake. The first time, they diagnosed the problem as a worn clutch plate, release bearing. The second time it happened, they are telling me the problem is the spark plugs and the AC coil. Anyone have any ideas?