agentdr8's post in Coolant Reservoirs was marked as the answer
The back reservoir is the cooling system header tank. I believe the level when cold should be about 10mm below the seam, and no more than 25mm below the seam. Any more than that and there's the potential for coolant to be expelled when the system is hot, as there's no room left to expand.
The front reservoir is for your charge cooler, and its max level is indicated by the line on the RHS.
agentdr8's post in Vacuum hoses when fitting BOE CAI was marked as the answer
You would be correct. The exhaust valve is controlled by another solenoid (VSV) mounted to the rear subframe, and it needs a vacuum source. I would connect the red and black hoses together. As it stands, you currently have a vacuum leak.