I used a genuine B&S part. I did not attempt to test the mower in the vertical position, but guessing it may very well leak. If we could determine the model number of the 190cc engine, the B&S website might show if the carburetor has been replaced with a different part number.
Replacing the 596505 carburetor with part #594058 fixed the sputtering issue on my mower. If you decide to try this, keep in mind that you shouldn't store the mower on its end (Smartstow feature) with gas in it, which isn't something I do anyway. My first priority is to have a mower that runs...
That is a good observation POM. The "non-Smartstow" Toro model is 21462 and appears to have the same B&S engine: 7.25 ft-lb Gross Torque* Briggs & Stratton® Exi 163cc (engine model is 104M020010F1) From the B&S website, https://shop.briggsandstratton.com/pages/parts-lookup#, the carburetor part...
Determine the B&S model number from the sticker on the mower and then use the "Browse Catalog:" option here: https://shop.briggsandstratton.com/pages/parts-lookup#
I have the same problem with my Toro mower, model 21386, and B&S engine 104M020254F1. I notice the sputtering on bumpy terrain and inclines. Also, I discovered the gas tank on this mower has an air inlet on the side that spews gasoline into the air filter. I went ahead and replaced this with...