So you a clutch pull relief device installed? This is a device that reduces the force needed to pull in the clutch lever. Have you tried making adjustments to your clutch lever? How much freeplay do you have at the clutch lever? Try this test - Get the bike up to about 40 mph in 4th gear on a flat straight level road. Yes, this is lugging the engine a little bit. Now, give it full throttle and watch the rpm needle. Does it jump up to a higher rpm as if the clutch was slipping or does it rise slowly and commensurately with your speed? If the former, then the clutch is slipping.