First, you don't "need" cold air. It will improve performance, but not enough to justify cutting a hole in the hood.
If you're replacing the hood (as I am), you can get a hood that has an air chamber in it (or modify one to add the chamber). Basically, the air chamber is a duct that is molded into the underside of the hood, which connects the air cleaner to an opening in the rear of the hood (facing the driver, not on the top). When driving, the bottom edge of the windshield has a lot of high-pressure, cool air (that's why your climate control draws air from the wiper area). A "cowl induction" hood will connect your air cleaner to that source of air.
But, it is not a way to fix a problem, and it is not something I'd worry about, if it meant cutting holes in a perfectly good hood. The gains aren't enough to justify it.
I'm curious why your mechanic thinks you need colder air.
FYI, the stock air cleaner for your car is an enclosed air box, with a pair of ducts which go forward to the radiator support, to get some of the air that is heading towards the radiator. If you really want cold air, and don't want to cut up the hood, just replace the stock system. However, all that ductwork will restrict the air so much that you will see less performance than you would with an open-element air cleaner.
Joe