2002 CR250 Bog off landings

Hello all,
I have a 2002 CR250 and its doing some strange stuff. I have had this bike for a couple of years now and I absolutely love it. Its has this really strange bog to it when I land hard off jumps. I posted a similar problem last year for my 125, the consensus was the float was set wrong. I checked the float this past weekend on my 250 and it was set to high (or low, it was set so it was not letting a lot of gas in the motor), so I figured I had the problem licked. But it did it again, and of course its not consistent. In late 2011 I rebuilt the entire motor, new crank, new bearings + seals, then crashed my brains out a week later so it sat most of 2012, I just started again late last year, it may have 10 hrs on the motor since the rebuild. At the end of last year it started to run really lean, turns out the flywheel side crank seal started to pop out, I am not sure if I put it in wrong, but with the new one in its seems to be just fine. Also yesterday I noticed that when I ran it hard down a strait then let off it would ping a little, like it was running lean. The plug looked like a chocolate chip cookie.
The motor is mostly stock, Wiesco Piston, Pro Circuit pipe+Silencer. 390 main, 32.5 (also tried 35 pilot with no difference) stock slider, stock needle with the clip in the middle.

Any ideas would be a big help

Thanks Again,
Stoop