FMF PP - with or without O2 sensor connected? + other issues

Hi guys! I'm new to the forum. So glad to see such a big and active community of wr's users. :) Me and my kid both have wr250r's and love them very much, but we started to upgrade them and surprises keeps on coming :(
  We have european versions with O2 sensor on the exhaust. I upgraded my bike to FMF powercore4 + megabomb + power programmer, did the flapper and AIS removal and now I'm playing with the power programmer settings to find the optimum numbers. So far, I noticed that promised power increase, also the fuel consumption increase :) (witch btw jumped from 3l/100km to 4,2/100km, depending on the settings on the PP) but the problem is that no matter the settings on PP(even left on 3-2-0,5-8-4-4), from time to time, the engine chokes when cruising at different speeds, just like he run out of gas. After I release the throttle and play with it a few seconds, everything is back to normal. Most frustrating was one time when I was engaged in a long and very steep hill climb on off road and the bike choked in the middle of the hill climb for no reason.I mean I did not kill the engine, I was constantly gaining speed and I had pretty good grip. It just fellt like I run out of gas again but the gas tank was full. Of couse I remained on the bike in a very dificult angle and the big surprise was that the bike was now acting like she had a bad battery. She doesn't wanted to start in that angle, the electric starter motor was working wery slow, just like with a bad battery in the winter and somwhere from under the saddle I could hear a loud buzzing coming from a relay or something, in the exact time when I was pushing the starter button. (this buzzing I experienced before from time to time on my old xt660z tenere that I had, but didn't find the reason why she did it, too.) Now is the first time with the WR. After I turned the bike around and went down to the base of the hill, the engine started normally. And another thing is that after this episode the electronic cluster was reseted probably from the loss of power. Today I checked the error codes history from the diagnostic mode and found code 030 memorized(ignition coil). I erased it and it doesn't appear again.
 I will greatly appreciate any thoughts anyone might have regarding this strange behaviour. And do you think that now, with the PP installed, I should keep the O2 sensor connected or not? (because I have it welded back on the powercore4 muffler)
  Thanks in advance!!!

Try checking the battery terminals to make sure there tight.

I figured out the buzzing noise. I read that is coming from the starter solenoid relay when the battery does not supply enough power for the electric starter motor to start the engine.
The question remains: why the engine chokes with the power programmer?? My setings was 3-4-0,5-8-1-1, so nothing extreme I'd say...
I never had any problems when the bike was stock.

Sounds like a known bug with the FMF Power Programmer that I've had, myself.
Read this:

https://wr250rforum.forumotion.com/t7636-cutting-out

I would 110% agree with the above as being the "choking" issue......
you simply just need to set your 5th number to 6 and it will be all good.

Also my bike is the Euro version with factory O2 sensor and after quite a bit of experimenting i've just ended up leaving it in place & connected. No problems after several 1000K's with FMF programmer.

May also be worth checking and adjusting the factory CO setting slightly.

Cheers.

Thank you all so much.
In the mean time I read myself about the 5th number issue. My problem fits the description indeed but it's a shame that we can't use numbers below 6 because I really like the 5th nr set on 1. I know that many don't like it, but I like that instant response when I open the throttle. And I don't see any connection between the 5th setting purpose and the type of problem that it causes. It's a serious bug. FMF/Dobeck should investigate this.
I will use 6 for the 5th setting anyway and I will let you know how it will perform.
Thanx again.

Sorry for the late response. I tottaly forgot about it. Yes, setting the 5th nr to 6, solve the problem.