Outer Limits 4x4 Board

Got a GQ Wagon with TD42, DTS Turbo Kit, Safari Front Mount Intercooler Kit. No A/C Condensor fitted.

Temperature is fine at idle or around town (sits under 80 degrees)
As soon as you hit the highway or get up in the revs goes straight up to 95 - 100 degrees..

Pulled clutch fan and fan off. Put twin thermos inside radiator sucking air. ran good but got too hot under load.

Put brand new clutch fan, and fan back on and fan shroud. Put 82 degree thermostat in. Removed thermos. Got too hot on highway....

With clutch fan, fan, shroud and twin thermos on outside pushing air.. gets hot on highway...

best setup was no fan or clutch fan with thermos pulling air..

any ideas???

Tried flushing block and radiator?? If it has only started gradually happening over months the this would be your first thing to look at (doesn't cost much either).

Retarded timing???