I drilled mine by hand and tapped them for 1/4-20 x .250 long stainless steel button head cap screws. Its very easy to do and they hold much better. You need to start the tap and after you get all the threads started, grind the bottom of the tap flat so you can get it to a good depth. If you do not know how to grind the tap, I can throw one in an envolope and send it to you.
That is one of the worst things about the Precision slic Intercoolers
I drill and tap the holes to 1/4-20 and use a 1/4" long stainless bolt and then add another nut to the underside of the bolt head. Then I tighten the nut onto the bolt so the flats align. That way it is very easy to start the bolts with my numb finger tips. (Sucks getting old I tell you!!!) I have a starting tap and a bottoming tap set. But you can grind a standard tap like Coach suggests.