Just drilling some small holes in the bottom of the airbox with a drill bit. People do it mainly for the noise. You might get a bit of heat soak but shouldn't be too much if you don't go silly with the holes. I've drilled the bottom of my LCR box with 9 x10mm holes. Not fitted it as yet but I do have much bigger airfeed sorted, smoothed box and panel filter.

Airbox1.jpg
 
Only 9 :lol: I did 50 x 10mm holes on mine :whistle:
I not noticed any bad effect's of hear soak and it does sound nice ;)