Problem with Yaris aftermarket parts manufacturers

[GMKing]

I've been looking around for a few good hours now and I haven't run across a single body kit that was tested for drag coefficient or even a boastful claim of being more aerodynamic than the stock body pieces.

Nor have I come across any performance parts that are tested for hp/tq gains, at all.

do all these manufacturers just assume that the consumer is going to buy the product with no regard to whether or not it will produce any sort of benefit?

or have I simply only run into crappy manufacturers who don't seem to have any care in the world for quality assurance? if you know of any manufacturers whom test their products and advertise their finding's please, post them up and let me know. turbos and superchargers aside, of course.