X trail mods

Luke I find it unlikely that you could get %5-10 more power from the exhuast.
If it was that easy the manufacturer would have them already fitted.%10 more power from an exhaust change would be a dream gift to a car manufacturer who would have the bragging rights over all competitors.

Modern engines are at near capacity when new and unless you spend a bucket load of cash redesigning everything then you are better living with it until the next one comes along

As to the criticism of your choice of 4x4 ,I think you are a little more honest in your reasons for purchasing this type of 4x4 than many who have purchased the largest and heaviest 4x4 tank only to never leave the shopping centre car park.
My landcruiser gets a good work out once a month or more time permitting but its not the daintiest on road and I can see the sense in a smaller softroader type of 4x4 in terms of economy and ease of driving.

Luke,
i don't know how far you want to go, but I remember Suzuki and some Lada Niva, (now there's a 4 X 4 to argue over!), owners used to run their intake through the firewall as snorkels for these vehicles were not avaliable. Rather radical I admit but it's up to you. Will probably find with a petrol motor and all those electronics that it would be better to set yourself up with a tarp over the front of the vehicle and on the entire bonnet to create a bow-wave through deeper water to keep as much dry as possible. Used this method for years on my petrol MQ Patrol with few problems, ie, I never got stuck due to water in the engine bay area, and for any of those knockers, have photo's where water over the door handles with a 2" lift fittted. it's as much about technique as preparation. Hope this helps.
Rolande
Rolande