MUHAHAH!!!!! I've been waiting for this subject to come up for a long time.
Hehehe. I used PLIERS. It's easy. Remove the splash shield and all, lay under the car and pry the metal down and out. The metal bends alot easier than you think. I have done this for CAI installs on a '93 XE, my 91 SE-R, and my 98 SE. It was fun, and easy. It should take like 15-20 minutes till you get the hole big enough. Get some big strong gripped pliers for the job.
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Jordan White (Stormy)
'98 Sentra SE(R)
Hotshot G3 Header, Hotshot CAI, JWT s4 Cams, KYB AGXs, Eibach Sportlines, Courtesy F&R STB's, ES Mounts, MOMO Shifter, Nis-Knacks chrome projector headlights and clear corners, 205/50/15 Pirelli P700Z's on SE-R wheels, 205/40/17 Kuhmos on 17" Borbet Type S's for the summer
15.1 @ 90mph at Englishtown, NJ - 14's oh so close