I have a 2009 Argo Avenger 750 efi with a Kohler lh775 which is fuel injected. I got the Argo from a friend for a real good deal because it runs pretty bad. The engine cranks and starts easy but it has low power, the engine spits,sputters, and backfires. I'm getting codes 34 and 31, I replaced the exhaust oxygen sensor which is code 34. Code 31 says it's running to lean. I'm not sure where to look for the problem so if anyone can help I sure would appreciate it thanks.