Another check, as already referred to:

Disconnect the throttle cable from its stud on the carb.
See if the carb's linkage closes, then see if the cable end goes on smoothly or you need to crack the carb open a bit.
Might have to lengthen the cable a little.
I've had that happen even by just pulling a carb & reinstalling.
Also, if the carbs have been off, see if the butterflies are all closing with no interference from the intake.

As for running a PCV valve & breather, that's good.
There are adjustable PCV valves on the market if you want to fuss with that, some guys really like them.