You are missing my point. I never said all performance parts are useless. Many sold out there are nothing more than bling and/or snake oil but there are many parts that actually real, performance parts. The debate we are having about intakes and exhausts fall into this category as well. Yes, you can mount up a great exhaust system and it might actually provide some benefit without doing anything else. Generally, a benefit that one would only see if they did before and after testing on a dyno. Installing a great intake that is properly plumbed to the outside air, same thing. Combine the two and things start to get rolling. But for maximum benefit, work also needs to be done on the engine. Like porting and polishing, perhaps a tune, a better intake manifold, so forth and so on. Any real horsepower gains are not going to come easy and cheap and certainly not by just bolting on a couple parts.
A lot of "cold air intakes" do little to help and actually hurt and just make more noise at the front of the engine. A lot of "performance" exhausts are the same way or only provide a benefit if the rest of the engine is upgraded or customized to match. Aftermarket companies are in business to make money and sell products to keep making money. If all they need to do is take a hunk of plastic tubing, throw a cone filter on it to make people want to buy it, great for them. They'll take maybe $40 worth of materials and make a $160 profit by telling someone who doesn't know better and likes it because it looks cool that it is a performance intake. Buyer beware is still very much alive and well in this day and age.