Just a hint you might try to check cylinder balance. (before you give up and throw in the towel at Briggs))
Slide the spark plug boot back on both spark plugs so as you can ground the spark plug tips while the Briggs Intek is running and have your IR ready.
Ground each individual cylinder at first while the machine is idling and check the rpm drop by ear. The cylinder that drops the rpms most is the stronger cylinder. Ground the left spark plug tip and let it run on just the right cylinder while monitoring the temp then do the opposite. I suspect the cylinder that is the hottest is the lean cylinder, rich on air and lean on gas. Do not pull the spark plug wire off to kill the cylinder, ground the tip.
Pulling the wire can ruin a electronic magneto.
I'm not saying you have a bad carb, but them dual throat Nikki's, one throat is for each cylinder.
I was given a Briggs Intek recently that was scrapped because no one could get it to run correctly.
When I got to checking the left cylinder was dead, good compression and spark.
I swapped the carb with a old carb and the problem swapped, right cylinder dead, left ok???????????(that told me that both carbs were bad and I was lucky they were opposite side bad) When I went to cleaning the carbs I found both had bad o-rings and could not take two and make one because they were built different at the H jet area. A OEM Nikki was priced around $200 so that was a no go and a OEM complete kit going by the number stamped on the carb casting was expensive.
I bought a $15 China clone carb, installed and got both cylinders running but the carb itself was erratic idling. I could have sent it back to Amazon prime with free shipping but decided to carefully peek inside first.
Removed the clone carb and when I removed the bowl it looked same as one of the other bad Nikki's, so I used the $15 china clone carb as a kit for one of the bad carbs transferring the completed H jet emulsion tube and it's jets and gaskets to the bad carb and got a good run.
Also I install paper gaskets (that I make myself) on the plastic intake manifold where it bolts to the head. I do not trust re-using the old rubber gaskets for a good seal. I just leave the old rubber seals in place on the intake manifold but they can be discarded. I think maybe some Nikki carb kits now come with the paper gaskets for this area.
At least I knew on this twin Intek I had a bad carb issue that was causing the engine to be weak on one cylinder. (not just guessing at the issue now)
My point being is those dual throat Nikki's can cause a INtek engine to do some weird things AND THE O-RINGS SEALS INSIDE HAVE TO BE IN GOOD SHAPE to seal passages, etc. (and they are not all the same internally even though they look same on the outside)