Anders, you need to get the Fel-Pro 1233 set.
The "hole" is the heat crossover. You need to make sure it seals, or you'll have a heck of an exhaust leak.
Most of the Pontiac guys use thin metal block off plates, which come with the Mr. Gasket intake set, not the Fel-Pro set. The Fel-Pro gaskets are higher quality.
Blocking off the heat crossover is sort of standard thing all Pontiac guys do, it allows for a cooler, denser air charge by keeping heat away from the plenum floor. But if you don't want to block it off, make sure you get the Fel-Pro set.
Also, if you haven't worked on a Pontiac before, make sure you use the rubber o-ring at the front of the intake to water pump, and use some silicone to seal it. Lots of guys forget that, or don't use silicone/gasket sealer along with the o-ring, and they end up with a puddle of anti-freeze on their valley pan cover.