The majority of the FAST video's the bikes are modified with added air filter, exauhst and rollers. Also you will find the riders are fairly small and/or light.
I am talking real world with an overweight rider. Also all my times etc are sitting normally, no tucking in and/or crouching down. I am 0-60 at about 9 seconds, if I were to shave 100 LBS from myself I am sure I would be in the 8 second or under times (this is with DR pulley 20x12 14 gram).
I have the stock air filter but have the Lightech on order now. That will be a while as Canada was the only location I could order from and they are not in stock as far as I know.
I might consider a high flow muffler but it would have to be QUIET and in reality those two things do not mix. That is quiet and high flow! Because I am not doing the muffler I expect very little if anything from the air filter other than washable rather than replacable.