Re: strange bogging at 1/2-wot
For now I do not recommend reaming it at all.
You have not done any of the other checks or adjustments to even know if that would be beneficial or bad. Assuming that one thing must absolutely done without checking all the other common culprits first can run you in circles or make more unnecessary work for yourself.
"It's a chinagirl. It's a sometimes fun little engine that often will break your heart. It's disposable.
Does not come with a fortune cookie."