The radtec intercooler I have fitted to mine is designed to allow air passage to the rad also.

I bet the fins to your intercooler are very thin but compact robbing the rad of its cool air. You should have the setup i.e. rad/int designed by 1 company. Have a look at the fins on a genuine RS500 intercooler and you will see they are spaced quite wide to give the rad some air also.