Oil spitting out from my breathers

I wanted to get some input on this new issue. I am running a 5.9 with 9.75 compression, a roller street cam and EFI. The engine is new, with about 1600 miles on it and runs strong.
Based on a suggestion from my engine builder, I moved to a heavier oil (Valvoline 20/50 racing oil). After the oil change, I took it out and noticed my oil pressure was up 10+ lbs on a short run. When I got home and did a quick inspection, I noticed the K&N breather on the passenger side valve cover (I run a breather on both sides) was oily and there were small spots of oil around the breather. Not a ton of oil, but certainly a new development spitting oil out.
Wondering now if it was a mistake to move to heavier oil for a car that is a street-driven cruiser?