If you haven't made a purchase, and to all other readers asking the same question as the OP,
DO NOT buy the Injens.
I too purchased them for the lower price, the fact that there's minor cutting involved (a very small notch), and they offered them in black (my Z is black). However due to their location of the filters I've had issues with keeping them dry. They have been on my car almost 1 1/2 years, and every time it rains it reduces me to an irate "granny shifter." With even the slightest rainfall it throws my car into limp mode. So far I've found the only way to avoid the embarassment of riding a bucking stallion through a busy intersection is to upshift before the 2500 rpm fuel cutoff until I get to an appropriate gear (depending on posted speed limits).
I should mention that my car is at stock height (I didn't add coilovers due to this issue
), I always park my car facing downhill, and I try my best to avoid standing water. Some may ask, "If they're such a pain in the a$$ why do you still have them?" They're already on my car, and I'm never in the US long enough to worry about changing them out. Just thought I'd steer anyone away from experiencing the same problems.