A Tunit module is basically a performance chip. Our American cousins wouldn't be interested, as their Pathfinders would be petrol rather than our obligatory diesel.
The module just wires into the CPU circuit. It takes about 10 minutes to do, and increases the power to between 200 & 210 bhp, whilst at the same time reducing the fuel consumption. Magic really!
On top of the module is a 9 position rotary switch, which you have to access through a plastic cover and adjust with a screwdriver. Usually the unit should be set at 5 or 6. This is where I had it on the Navara. The lower the number, the greater the economy. The higher the number, the more power, for towing for example.
During a long road trip across Europe last year I was getting over 40 mpg on long motorway runs. It never dropped below 35 unless I was doing nothing but town driving.
I had the garage transfer it to my new Pathfinder on delivery. To date the fuel figures are nowhere near what I was getting in the Navara. However, as I have done less than 2000 miles, I don't anticipate anything good until the engine loosens up. I have 36,000 on my Navara & the engine has never been so smooth. This was asimilar to a Daihatsu Fourtrack I owned years ago. I was told it would loosen up at 36,000 miles. I thought it was total rubbish, until I hit that magic mark. I had already advertised it for sale, & nearly kept it because it was so good.