Related line: https://github.com/BuildCraft/BuildCraft/blob/7.1.x/common/buildcraft/transport/PipePluggableState.java#L49

Since it is creating new instances of the PipePluggable on the client, sometimes multiple times per tick, keeping a state on the client becomes impossible. An example for state on the client could be a rotation for rendering. I also need the direction of the pluggable to be persistent since I have to send packets from client -> server, and otherwise finding the pluggable on the pipe becomes impossible.

In general I would make them work like a lite version of a TileEntity, since the API suggests that you can have a state on the client.