I'd look at the RPM, should be fine for your application and will be fine if you decide to go with a bigger cam too. The performer's aren't all that better than the stockers, although they weigh about half as much being aluminum vs cast iron.
As far as the RPM vs. the air gap, I'd consider the weather and the type of driving you do. I got an air-gap because I live in California, and because of the weather here the majority of the time I'm not worried about the car warming up, I'm worried about it being too warm. Not sure exactly, but I'm guessing its quite a bit colder up where you're at and you'd probably be better off with an RPM. Then again, if you don't drive when its cold you'd likely be fine with the air-gap, and in addition to keeping your fuel charge cooler they're a better manifold. They're also taller than the RPM though, so if you're running a flat hood it could be a problem, and it looks even less stock than the RPM does.
