any car that runs a AFM (Skylines!) cannot run Atmospheric wankerized, look at me, whoosh whoosh, fully sick, where are the chicks, Blowoff valves.
The Engine reads air.. Inserts fuel. The Atmospheric blow off valve dumps the air before it gets the the engine.
Put the stock one back on, or get a plumb back BOV.
The other option is to get a Powerfc DJetro with a MAP sensor and then put your spinny twirly whoosh chicks hurricane atmospheric BOV back on, and you'll be fine.
So yeah..