When my 101 suddenly lost some of its power (I didn't note your issue of pressure out the carb), I right away took off the heads and found some decoking was in order but there was also a particle of carbon keeping a valve from closing.
I then took that as a opportunity to pull off the cylinders, have the local race machine shop very lightly touch up the valve seats, installed new valve springs, and while at it new rings on the pistons as well as take bore and valve guide measurements to see where things stood.
Maybe you have a buildup of carbon and loose bits holding up an intake valve from fully seating.
Bob
