Ok i'm planning on ordering a new TIP soon along with some upper boost hoses to change the look of the engine bay, but also want to start replacing some of the smaller hoses around the bay. Problem is i'm not entirely sure what they all do (and hence whether or not i should be changing them) or what size hose i need! I know i need 4mm id if i was doing the N249 bypass, are most of the hoses the same?? And what thickness of hose do i need? Is 2mm enough?

I've highlighted in red some of the bits i mean, unfortunately i dont have a pic with the cover off but if someone could explain what these do and what i need to change them that would be great



As always, any help appreciated!