i heard about these are they good??

Do a search for Power Now and there should be a whole thread about it. I recall it not being all its hyped up to be. I think it increases power a little tiny bit, but also reduces overrev. Usually, the hydrolic clutch is an easier pull, but the main thing is that you never have to adjust it. With bikes ridden hard, the clutch cable has to be adjusted during race because of plates heating and expanding, or clutch wear, but with the hydrolic clutch, you never have to adjust it.

The power now mod consists of a divider plate in the carb throat (we're talking about the same mod?)

The RB carb mod has that plate installed, but also some other modifications as slide cut for one.

I've not heard of a single kdx with the power now mod. Lotsa riders have the RB carb mod. CDave considers it one of the best mods for the kdx.

He is correct. (well, not that I've ever known him to not be correct!)

Contact ron (of RB designs) here if you have a question about his product.