For the best performance we want a straight shot from the beginning of the intake track to the intake valve, however other than the V-Rod Harley doesn't come close to a straight shot. Any time you make a bend in the intake track you slow down the inertia of the air rushing into the cylinder, so when racing we will not add any more distractions to the intake track. I said that to say this....street bikes are not going to suffer, seat of the pants, loss in power when you use the Heavy Breather....you might see a .5 or 1 hp loss on the dyno from the added 90 degree angle but if your not racing who cares about that 1 hp loss. I've seen a lot more power left on the table from exhaust choices rather than an air cleaner choice.
I did a study(dyno runs on a mule bike that was mildly modified, heads, cams, pipes, 98/108 95'') on the SE air filter kit, Zippers Filter, Dougherty Air Filter Kit, Big Sucker from Arlen, the Heavy Breather and they all performed within 0.50 hp of each other......the only filter that stood alone with a 2.5 torque increase and a 1.5 hp increase was a filter from a new company called ''Exotic''.
Bottom line and my point is this....for a street bike why not run the filter kit you want because the gain or loos from your choice is at the most very minimal.
Doc