yes i know it's when cruising, with the cooler fitted the airflow is RESTRICTED, and the fans AID the cooling, i'd say that's one of the con's of having a full front mount, it's going to restrict airflow, and the fans are going to have to do the job whilst cruising! your never gonna get a car will a full front mount that can cruise down a hot m/way on boost without using the fans unless it runs not allot of boost, and everythings in good shape and has sufficient airflow!

their are allot of things you can do to make them work less but their still gonna come on at some point!

I know fully what your saying, but your not seeing what I mean

things i'd do to aid it:

cut out as much of the bumper as you can
bonnet raisers
can get some product to put in the coolant
good water/antifreeze mix for summer
new/recored rad
wrap the downpipe in heat wrap, i know the turbo will still heat the rad up but its better than nothin
new header tank cap
stick with plastic header tank
fans inbetween rad and IC

prob more you can do but thats a start!

Could it be too much ignition advance/boost set up, as this heats the engine up far quicker/hotter when giving it some than one set up with less boost / more retard