The restrictor is actually kind of funny. The pipe comes with a red tape label over it telling you not to take it off because it 'makes your bike illegal!' - LOL.
It is this small - about 2" tube that is tack welded onto the port end of the pipe. It has a SIGNIFICANTLY smaller inner diameter than the main pipe and port....like, 3mm all around. = SLOW.
So, you just get a bigass drill bit, drill down about 3/8" until you got through the weld (honestly, it's just for show, in my opinion...Leo Vinci KNOWS people are just going to tear it out!) and punch it down into the pipe. Flip the pipe over and it drops out!