I too had a Toro, while it didn't do quite as bad as yours I was having to essentially mow my lawn twice whenever it was the slightest bit damp or long else it would choke and die. I would have to slowly cut the first row, then take half bites out until it was done, then go back over the hay rows it left. The thing came with electric start, which lasted about a month, the electric motor would turn, but it would not engage the engine to turn it over. The B&S engine ran great, I just couldn't get the mower itself to cut as well as I thought it should. The self propel belt kept slipping because it was right under the deck in all the grass clippings. At best it made the mower neutrally buoyant. The oil drain was right over the belt and required me to remove the belt guard to remove the plug to change oil.
I'm just a cheap asshole and did not want to buy another mower. I put up with it for 7 years. I got fed up, I'm just getting too old for this crap. I went out and bought a Honda HRX217HYA, all in about $1000.
Damn! The self propel can pull like a draft horse. I can set the speed so high that I can't hardly keep up with it, and yet it cuts just fine at that speed. It cut high grass without even slowing down. We've had unprecedented rain here, so it was tough to get a time when the grass is dry a few times. This thing cut right though it, high AND wet grass, just an occasional clump up. I would actually just flick it with my foot and it would disappear. I actually finished in the pouring down rain one evening and it still cut perfectly.
You may be like me and just can't bring yourself to spend all that cash. For me it was worth it. Due to the rain I've had to cut about every 3 days. It's made my life so much easier.