N80 is the charcoal filter solenoid valve. The charcoal filter is part of the fuel tank vent system: it absorbs fuel vapours while the car is not running and opens to allow them to be sucked into the inlet system when the car is running and up to temperature. (We're not allowed to emit any unburned hydrocarbons in case California should run out of breathing air).
The line you've shown isn't heading anywhere near the charcoal filter, which is on the nearside wing between the washer bottle and the cooling system header tank. The charcoal filter vents into the crankcase breather hose.
I don't have a V5 so am not familiar with the plumbing - however, if, as I think, that pipe is attached to the inlet manifold on the left, then it is part of the pneumatic system, and is tapping the inlet manifold for vacuum (have you got any pictures with more detail, more pixels so we can see a bit closer?). With holes in the vacuum pipe you are letting unmetered air into the inlet manifold after the throttle body, so it's uncontrolled as well. The ECU will be having a fit.
You've also compromised the vacuum source, so there won't be as much vacuum as there should be (This is a horrible statement: vacuum is an absence of air pressure. What I really mean is there's a hole in the pipe leading to where the engine is sucking air in, so there's not so much suck. If you see what I mean) Lack of vacuum will affect the brake servo and anything else that's vacuum-powered on your car. That will include the secondary air inlet valve N112, the fuel pressure regulator and the intake manifold changeover valve N156 (changes the manifold length).
As to where it's going, I think I can see a T-piece next to the throttle body, possibly heading off towards the brake servo or vacuum reservoir. The N112 and N156 valves appear to be mounted at the front of the engine bay next to the inlet ports, and the fuel pressure regulator is down there as well.
If this is the vacuum hose you really need to get it fixed, and find out why it's in that state in the first place, to stop it happening again.
Slight misfire, and shaking at idle? Something very wrong here, the V5 engine is the epitome of smoothness. Eliminate the vacuum system first. It may be a good idea to reset the ECU by disconnecting the battery for half and hour or so - make sure you have the security code for the radio first, though. When you reconnect the battery the car will run like a dog to start with as all the ECU adaptions will have been forgotten. Take if for a few short drives, switching off between each one, and including some national speed limit mileage. The ECU will re-learn the adaptions, and will hopefully run a lot better. If you still have misfiring, the next suspect is coil packs.