Is there a spark arrestor screen on the muffler? My chainsaw will do this and it means the screen is carbon'ed up and exhaust can't move through fast enough, so it can't breathe at higher speeds. Or maybe the muffler is clogged.

Yes Dan, the roll over valve can sometimes not vent on occasion. It's very odd, but happens. What happens quite often though is the fuel tank design allows bug and plant debris down in the outlet which can definitely lead to a starvation issue. The diaphragm fuel pumps can't overcome a blockage or a non vent situation.

So diagnosing a fuel delivery issue isn't difficult. Removing the inlet hose from the pump - fuel should easily drain out on a rider has the under hood fuel tank. If it doesn't, remove the fuel cap to see if it improves the flow. If it doesn't and the filter is clean, blow threw the inlet hose off the inlet side of the filter. Just lay a clean rag over the fuel fill neck with the cap off to allow the pressure to exit when you pressurize the line. Debris floating around the bottom of the tank, there is your answer.

Beyond that ensure that you are holding 12 volts at the fuel solenoid below the carb bowl and that the solenoid fully opens. Since the carb was cleaned and replaced (hopefully with an OEM carb) this isn't likely an issue with the solenoid itself.

Hopefully none of the corrections have caused other issues.

It still may be the anti backfire fuel solenoid. A Kawasaki FD620D 22hp in a JD 2500B greens mower was acting similar. it did end up being the fuel solenoid. What I did and you can try, is I hooked it up to another 12v source and marked where the needle went all the down. After watching it and letting it get hot, it would slowly raise back up. Deere wanted $120 for the part so I clipped the needle off it.

Also, are you using an OEM Kohler fuel filter? I remember hearing that aftermarket ones can cause them to act funny

Yt125 , right on with the fuel filter micron sizing with Kohler engines , very important to prevent fuel starvation at moderate and high engine rpm,s , however the fuel cap scenario definitely indicates a vent issue !

Dan- What fix ended up solving this? I am having similar issues and have replaced the same things you mentioned.

Check the fuel cap is venting properly . If the engine rpm increases with the fuel cap cracked then you have the cause !

Update. Sorry I took so long to post the fix. The problem ended up being the fuel pump line being blocked. When I had changed out the fuel pump I did not originally change out the all of the hoses. It was the hose leaving the pump. Just enough gas was able to get through the line on idle. However, when you increased to running speed the engine would stall out. It appeared to be some kind of plug...the engine runs like new again. Apparently, it had been there since purchase and gradually moved until the engine problems started.