Briggs 19.5 hp motor won’t operate past half throttle / overly rich

It's possible, I've never heard of it happening, but after more research, it seems there are alot of problems with the 793880 cams and the cams it replaces, Taryl did a video where he replaced one, and the mower would run okay, but be popping and backfiring. Worn cam lobe was the problem....
When the cam timing dots are lined up on the crank gear and cam gear, there should be no pressure on the valves and be able to pull that cam out easily on most engines, if the gear slipped, i suspect you would have to find the sweet spot where it is not lifting a tappet.
But looking at a stock picture of the cam compared to OP's cam, the lobes look to be in the correct position.
 
So how would the piston get 1/2 to 3/4" down into the bore with the dots lined up? Crazy.... The piston should be TDC with the dots in line right?

slomo
 
Original engine. Never opened up. The marks aligned each revolution but the piston wasn't at TDC. I wonder how it happened
 
I think all the new 793880 are supposedly better made, I think the problem was an issue with materials, too soft and wore quickly.
please correct me if I am wrong.
 
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