Black Gunk on screen and inlet jet in 5 year old Toro Snowblower

Last year, as I was cleaning my driveway off with my snowblower and it up and quit. I couldn't get it started again so I took it to the small engine shop. The service manager told me the carb in my snowblower was plugged. $50 or so later, I got it back and ran it the rest of the snow season. After the season was over, I ran it out of gas so the carb was supposedly dry. This year, I got it out, filled it up, and tried to start it again. Again it wouldn't start. I pulled the spark plug (which looked good) and put some gas down the cylinder. It started, then died. I pulled the bowl off of the carb. There was a screen that came off of the inlet tube. The screen had some black gooey gunk in it. I cleaned the gunk out of the screen. Then I unscrewed what I would call a jet out of the inlet tube. It was completely plugged. I used a pin and cleaned the jet out. I put it back together and started it. It started very easily on full choke. I let it warm up a few minutes then took it off of choke. The engine then started to surge. It would drop in rpm, then pick back up, then drop off again. When I applied the paddles, it seemed to run better. It will be good enough for this snow season, but I have a coulple of questions:
Is there more that I have to clean out? Where did the gunk/sludge come from? Would it have come from the hose?. The fuel and fuel tank is clean as far as I can tell and has a fuel filter as well.
Thanks.
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Yes
Bingo!
The fuel and fuel tank is clean as far as I can tell and has a

Check all the rubber stuff associated with the carb, hoses, gaskets, diaphragms (like in the vent cap), whatever. Bits of crud will hide in places you can't see, so be as thorough as possible. Replace any tired parts with top quality items. Running it the season in the present state of tune could be a bit rough on the engine.
Joe
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