Price is one factor. And if there aren't a lot of proven gains for an exhaust, most people will look instead toward one with lots of dyno support such as Fast Intentions.
Exhausts like Meisterschaft and Amuse are exceptions to the rule since they have such unique sounds that any lack in performance compared to other exhausts is easily excused. And sub $1k exhausts are overlooked because "You get what you pay for" pops up, even though it may not always be the case.
EDIT: BTW the Injen exhaust has the be one of the rarest 370Z exhausts. Almost no info at all on it for some reason.
__________________
@stupidtoycars | My track vids
09 7AT|MCS 2WNR|Topgunz Rotrex|Ecutek (Eugene)|Maxxis RC1|Titan-7 TS-5|OSG LSD|Rear Mount Derale Oil Cooler (WIP)+25 Trans Cooler|Fismo|G-LOC R12/R10|Zeta III L|NLR Wing and Splitter|CJM Pan and Fuel Hat|Radium Surge Tank|AP Racing CP9668
|