Perhaps this guy is in California where the emission laws are a little strict.
I honestly do not know. This does not strike me as a way to improve performance. It will create more backpressure into the fuel tank and exhaust port of the engine, but I do not see this as a good thing unless you are running a huge lenght of exhaust manifold or extremely long backpressure line to your fuel tank...even then, I can think of no real gain.
Perhaps this was just a make-shift exhaust plug to keep it from dripping on his table. Note that it is not zip tied to the stinger.
Maybe he likes ruining air filters? Some sort of vendeta... I can't believe he's trying to quiet it down, the 2.5 stock exhaust is the quietest one I've run to date with my savage 21 stock being the loudest.
:idea: I guess he is selling for someone else and put the filter on the pipe (he has no clue what he is doing) to make it look better before taking pictures.