New lawn care services owner, I have a backup mower (old reliable is what I call her, my Kubota) but I really need my SCAG Cheetah running right again. mower has 24 hours on it. about 2 hours ago it would begin to sporadically backfire and begin running very slow, bog down horribly at slow speeds on minimal grass. (assuming it was only running on one cylinder) it would run great, then run horrible, no idea what the problem is. we have changed plugs, tried running 93 vs 87, ran sea-foam through it, no change, still very sporadic. when it runs like crap, I get back fires pretty consistently (assuming the fuel isn't detonating in the cylinder) my only thoughts are coil/s Dealer thinks it could be, but he believes it is the fuel that has caused a buildup on an exhaust valve and it's sticking.....seems like a lot of buildup for such a new mower with minimal work, always ran shell/chevron fuel through it (87 octane, but the E10 crap as it's all we have) we just did the first service on the motor as we were eliminating possibilities. oil was pretty clean actually. thoughts? opinions. we currently only have about 3 jobs for each month, but most are larger flat and about 4-5 acres each (wondering what you guys charge per acre as well?) thanks for the help fellas, I love my cheetah, she was expensive but makes large jobs VERY fast.