The pipe around the intercooler is 56 mm it is very tight, i had to drill up from the front vallance throgh to the intercooler with a 75 mm hole cutter, and then with an extention bar a 60mm hole cutter up behind the head light be very carefull off the intercooler not to catch it when drilling. The 75 mm hole underneath will also let a bit more air in for the intercoller and i also drilled the rest of the holes through on the fog light suround to the right hand side of the light for more air to cool.