PVC breathers on valve covers

but if you run a full exhaust with mufflers you create back pressure back into the engine.

What? Who told you that? Let's see the significant numbers, as they pertain to a PCV or EVACS .

OP
I ran two evacs on the street, but found that they work really, really, well. So well that even just one wanted to empty my oilpan through the valve cover. Even after reengineering my baffles, it still pulled enough oil under certain conditions to leave a cloud of oil behind me.I imagined a system to get around that, but,in the end I went withe PCV instead. As an aside, a PCV provides a good amount of idle-air-bypass, to help set up the T-port sync-up.I wish the carb people would engineer a nice adjustable idle-air-bypass circuit.I think it would help solve a lot of problems for newbes.