YZ250 clutch??? help

Hi,

I got my bike 2 month ago and I've riddin it several times.
lately, I've started to feel some problem with my bike.
It feels that 1st and 2ed grears aren't strong/reactive
enough like they were use to be before.
The clutch works when I release it one first gear, but sometimes, especially going up hills (not too steep) it feels like the engine is working hard (in 1st and 2end gear) and the bike doesn't really "kick" anymore.
Is it a problem with the clutch?
Could it be the gear?
If clutch,
Which clutch should I get? an Yamaha OEM is good?
or should I get: - Barnett - Dirt Digger Carbon Fiber Clutch Kit
or
Barnett - Dirt Digger Kevlar Clutch Kit
or
is EBC (DRC Series Clutch Kit) better ?
Thanks

Thanks. I will check it.
If it's the clutch, any recommendations?
Should I stay with the OEM or get a diff. one (e.g Barnnet, EBC, Hinson)?

Thanks again