Hellp my kohler 26 efi is having a fault code 34 which is fuel system/oxygen sensor, I don't think its the oxygen sensor because it was replaced two years ago. I had just replaced the crank case seal so the engine was ripped out and wile it was out I had replaced the fuel filter. I put it all back together and now its throwing a code 34, and after it throws the code it runs terrible with a miss, and also looks like it runs very lean on fuel. (Sparkplugs are black) if the computer is reset the mower runs great, until after 15 minutes of running it throws that code again. Any ideas on what it could be, I'm guessing it has something to do with electrical. Thank you, any thoughts will be great!