I'm from pittsburgh and its surely not illegal to ride these things in PA. You just messed up big time and pissed some people off. I actually idled my bike next to a couple cops who were standing on the sidewalk, they didn't say a word to me. Just keep your cool, you don't own the road.
to answer your question, it is not illegal to ride these in PA under these circumstances:
The bike is under 50cc's (which mine is not)
The bike must have pedals
You must have a drivers license class C
engine may not exceed 1.5 brake horsepower
yes, these bikes are loud, my friends can actually tell when im nearby by the sound of my bike, its very distinct. I mean you can only hear it from a block away, but still the things loud.