Sorry Tarnia I missed it was a turbo, the intercooler can clog up with oil sludge from the emission control system. It could be clogged or flow restricted by bash plates or a combination.
I cleaned mine out with petrol, then flushed with meths and sat in the sun for a few hours before putting back in. If you don't get a heap of discharge then it probably won't be that, however check the radiator in front of it that it isn't clogged up restricting air flow. Failing that maybe take the bash plates completely off to test if that fixes it. If it does then you'll need to do something to rectify it.
Perhaps try a Pajero forum, it's probably a common thing.
Also if removing the bash plates fix it getting a bigger intercooler will help.
Edit if you clean the intercooler, make sure as hell nothing volatile is in there when you put it back in, thats why flush with meths well and leave in the sun for a while or run with a blow drier for 15 min.