all depends on what mods you are running
- itg maxogen/forge (twintake) intakes will benefit from 'fully' open fog grills where by you remove the plastic bits which comes attached behind the open fog grills as this will allow more air to enter the void behind the headlight where the itg foam is positioned
if its just a craponio/dbilas/bsh etc then dont bother
- if you have a forge twintercooler (upgraded intercooler) then the open fog grills will not fit unless you remove the plastic bits which come with it, due to the additional pipe work on the forge ic
i ran mine fully open over the winter months as I had both the twintercooler and itg intake, I did notice more muck in the engine bay but Im not really bothered by that. one thing which did catch my eye was when driving in heavy rain with 'fully' open fog grills was that the foam on the itg intake was often wet after a long drive, it shouldnt be too much of an issue with the foam been oiled but i would be a little concerned with a dry filter like the backdraft (itg copy)
i did swap back to the normal fog grills for a bit and i am sure my butt dyno noticed the lack of air reaching the itg intake so went back to open again