m4ttyrs

hiya guys. just got some stuff done to the cossie, injectors, head gasket, chip, closed loop ect. Briliant job run great for a while but its started missin a bit now under boost and running lumpy on startup sometimes, its running around 380bhp and im on the standard oil breather. Now i know that i need one and im going to order one tomorrow but would this cause the car to run like that? Also any suggestions which breather, nothing fancy just to do the job? thanks