Hey Mate,
Take a look at the link I have above no other FMIC on the market supplies such detailed graphs and reasearch into their product as the HDi group have. The cores are very big and you do need to do some cutting of the bumper to fit it but overall the kit provides absolute minimal lag and majority of people have said you cant even notice any lag or pressure drops with the HDi coolers, it’s a very well made kit that might cost a little more than some on the market but I can assure you it is a quality kit and you will have a great smile on your face once its fitted on your GT.