Outer Limits 4x4 Board

I have a 2000 4.2turbo diesel have just fitted a factory intercooler and bonnet scoop and found its overheating when I go up hills and in stop start traffic. Doen't get over 3/4 but it cuts out the air con, any ideas what's could be wrong and how to fix it.
It did do it once before the intercooler was put on but that was climbing the Jimna range with 1t camper on the back

Anyone got any ideas