I have a bad misfire with my xt350 under load/full throttle, have replaced plug coil & lead, any advice welcome. Thinking it may be a problem with cdi?

Have you cleaned out the carb yet? There is a product they sale here in the states called Seafoam. Try that out. It comes in a spray or poor it in your tank. The best stuff on the market and it wont eat up your carbs.