I've run my T2500 steady for over 3 seasons. I always use premium fuel and Opti mix. I've had some carbon build up problems and so last season I changed to Amsoil. It ran fine most of the year and then near year end it really started to have carbon build up again. It will be running fine and then just die. I have to pull the plug, spray some cleaner in the cylinder and let it sit a few hours. When I install the plug and it fires up, sometimes it spits out a carbon chunk, then runs fine for a while. I only run 80 twisted string but I do like it a scosh long. Do'nt run a guard. Any ideas?