Yea, i am getting really irritated now.
my headset is perm Dimmed.
i reverted back to FW .255 and i just tried PT .249.
I already stopped all process of Pitool in task manager.
i already uninstalled and deleted the install Dir of pitool.
I already Deleted ALL pitool user/appdata Folder(local, locallow, roaming).
And restarted multiple times.
nothing is fixing it, and now my headset is stuck Dimmed/dark and color washed…
this is unusable now.
Did you reboot windows?
Not sure otherwise save finding that file that stores changes sent to headset. May have FoV options etc in it.
Yea, i did say i restarted my PC multiple of time. 
@Heliosurge
Just installed. Though will only have time for a quick check on 8k atm.
Unfortunately no firmware updating seems to be happening on 8k. 
Okay, i might have a fix.
If my idea did indeed work.
i want you to pin this for those looking for a workaround. @Heliosurge
I had just installed pitool .144 where the backlight setting was not removed yet.
and set that to high.
90hz is fixed for me, and not dark.
so, now i am going to go back to PT .255
and try it on there.
IF that fixed it, i will reply again. 
@Heliosurge
Pinned topic for 2 weeks in case a new pitool comes sooner
IT WORKED @Heliosurge
holy crap, i did not think that would work,
But, my idea did work.
Now that my theory did work.
Then, we could do that with the new firmware too.
So upgrade to the 144hz FW
go back to pitool .144, put brightness to high.
and go back to PT .259, and it should work.
Wowsa. Just tested and confirm 120hz at full normal fov! Still to test 144hz. Well done Pimax! Bravo! That’s with a 5 meter extension as well. It’s still janky to get it to connect sometimes (think i’ve always been just on the limit with the extensions) but once it’s connected it’s working. Also noticed the improved Pimax icon in steam vr.
Hello everyone I have exactly the same problem as KING TODD. It is dark and it dim. I also deleted everything and restarted and the problem still remains.
Awesome while no new firmware on og 8k seems nicer though only a quick check in Gunjack.
2 posts up Kingtodd prescribes a fix
Thanks KING TODD worked.
i think the gpu slider is working now
Okay, my theory applied to PT .259 and FW.264
So, if your panels are indeed Dark/Dimmed after upgrading to FW .264
Go to PT .144 and change the backlight brightness to High or medium.
Then go back to PT .259.
It is fixed and i am using 144hz.
P.S
I almost had a panic attack, as when i was upgrading my FW back to .264
the FW failed on me, and i could no get it to flash or detect it anymore(even DFU mode).
then i change USB ports and it worked again 
Anyways, after all that.
Seems 144Hz is fine after using the PT .144 trick.
So, this should be pinned for those looking for a way
@Heliosurge
So, What we NEED in the next Pitool.
is the Panel Backlight put back in, so we can manually change the panels to Low, Medium and High.
TESTING 3 Songs in Beat Saber and works without tracking loss for the first time on my 5k+ 203… WOW!
I’ll keep trying…
Thanks you! @Alex.liu team, and Valve no doupt this is a step forward, I hope you manage to solve the problem completely for everyone. I will continue to report any losses, but this promises…
Oh man it worked you are a genius. So maybe in 259 they added some code that makes the backlight low but we do not have the option to change it like we did back in 144.
Anyways can’t believe you figured that out but you are a lifesaver.
My guess is that the backlight level setting doesn’t work for one of the newer headset models, so Pimax just removed it from PiTool. Apparently, PiTool doesn’t reset it and the headset will use whatever the last setting value was.
@neal_white_iii
They need to put that option back to be honest and code it for use on headsets it does work for.
If this is going to keep happening, this is needed.
As, Whatever level they set will stick to ours, And it’s causing issues like this.
Then we have to go back to one that has it to set it to what WE want/need for it to be normal again.