I got an 06 KXF that i bought used. I changed the clutch and the oil, changed the air filter, and threw a new plug in it. It runs for about 20 minutes, REAL good, then it will just bog and shut down. What could be causing this? I think its overheating, but the coolant is good and there are no signs of actual overheating. Just wanting some opinions and seeing if anyone else had this problem yet?