exhaust system pcv?

I have that same setup; I installed mine in the collector on a set of Dougs D450 headers. I have always found that you would need to install them IN the collector. I am running Borla mufflers dumped at the axle, and an X pipe, all mandrel bent 2 ½ system. At idle, there was a MASSIVE vacuum on the hose going to the valve cover. As I would increase throttle, the system would stop sucking, and blow backwards. I attribute this to having a slightly “restrictive” exhaust. I do not use the system anymore because it is really meant to be for a very free flowing exhaust. When I run my car open header, it works GREAT. Just my 2 cents worth.