Hey guys.....Have a 25 hp kawi on a scag..Approx 1650 hours...It has been to my local mechanic twice for engine issues and all have been fixed. The last month or so I'm losing torque on hills and thick grass and when engaging blades..It runs choppy for first 10 mins or so..Also noticing a gray-black exhaust when engaging the blades..What do you think?? Time to rebulid?? Could it be a fuel pump issue?? Electric gremlin?? Just wondering Thanks!!!!!!!!!!