Have a 2 -year-old Toro SW5000 Timecutter which has run more or less fine to this point, but this summer, and in just the past few weeks specifically, I have noticed that the engine will lug more than usual under load, which will sometimes trigger the mower deck to disengage. These two things do not always go together, I noticed today that the deck would disengage when not under a particularly heavy load, but it is happening with more frequency. I removed and cleaned the deck and sharpened the blades, and have kept clean oil, clean air filter and checked spark plugs, so all seems fine there. It is as if after two years of service, the mower just doesn't quite have the power it needs, with the result that the mower disengages probably 6-8 times over the course of 40 minutes of mowing (and in not particularly long or think grass). Any ideas on this? What am I missing? Thanks!