Too much air pressure on valve cover breathers

Is this your first NOS engine? Did you break it in on a dyno? Did you use a blow by meter while on the dyno?

I'm not so sure that you have a problem, my guess is that is just how it is going to be. First of all it is a stroker so you have a lot more air pumping around. Secondly you have it set up loose for NOS. Do what other people do. Either a vacuum pump or run remote puke tanks.