Hi Yoshi,
Fitted a Kenlowe to my 2.5TD about 18 mths ago. I also fitted an Allard intercooler and lagged the exhaust manifold and down pipe. I was hoping to get better mpg from every mod but apart from about a 10% increase (about 2.5 mpg) what I got was more power, power, power... Now pulls like a train, no need to drop out of top gear on hills and will even pull smoothly in top in town at 30 mph. I reckon you get more mpg only from dropping weight so dump the roof rack, steering guard, hi-lift etc Also don't forget if you put a temperature sensor in the top hose to fire up the fan it could still kick in when you're in water unless you fit an isolator switch on the dash.
Happy wading!