SEDUCE

hey guys i am having a bit of trouble with my ute, when i drive around town the cooling system is fine (sits just under 1/2 way) but when i go on highway and if i put the air con on it goes up to 3/4 mark, it has a new radiator water pump an't leaking or any other leaks, thermo fans work but if its hot and i turn off car the thermo still goes for a while then turns off???
i am thinking it has a blocked thermostat what are your thoughts cause i have asked a few other mechanic mates and no one knows anything?
i did notice that the gauge comes down a bit after i go off the high way but only comes down a bit???
any help guys would be good thanks alot

PREDATOR-Z

Blocked air to radiator or not enough
Thermostat (if thermo blocked, the hose leading to it will remain hard while hose from pump to radiator is soft), bubbles in radiator
Tuning of fans
Blocked water passage in block (can be tested via coolant analysis and same issue with hoses)

SEDUCE

Yeah Both Hoses Are Hot And Feel Like Boiling Hot ????
It Has Been Fine Since I Had Deads And Cam Done Then Like 2 Months Later It Starts Getting Hot?