HMD Plugin lag in cardboard

Can anyone help to find why HMD-based plugin have some serious input lag?
It must be some bottleneck, i suppose.
I’m comparing same app with just background cubemap in unity build, simpleHMD plugin and Nival Cardboard plugin. Use it because ios and android4 building capability.
In Nival plug-in everything looks fine, but there’s some serious input lag, around 25-30ms, somparing to 10-15ms in unity. Standard SimpleHMD somewhere in the middle.