Ah a Scotty Kilmer fan. Explains a lot.
Anyways, when you say that the manufacturer added in the restrictions to optimize the engine performance, that's not all that true; at least in this case. A Corolla is an economy car so obviously the engine was built to be as efficient as possible. This means that there were restrictions put in to some of the engine components to reduce power and fuel consumption. Therefore, getting rid of these restrictions will increase power somewhere (I'll add to this in a bit). Just like I said, simply installing an intake or exhaust won't give you all of it's performance benefits right away as the computer will compensate for these parts but there is a limit to what a computer can do with an aftermarket part. Also, these aftermarket parts, if designed well, will be able to show their benefits even with the computer trying to correct it. Now, doing these mods to a car with an already well designed intake and exhaust system may not show as much of a benefit and may even make you lose some power. In this case, an intake and exhaust may not seem beneficial however, a Corolla does not have a performance designed intake and exhaust from the factory.
Now, even when you have a performance intake and exhaust system with a proper computer tune, you still shouldn't be expecting 50+ horsepower from just these mods alone. In fact, most modifications to a car don't just give you a huge amount of power just like that (at least when modding a naturally aspirated engine). If one is looking to get a great amount of horsepower, then you'd have to do much more than just replacing the intake and exhaust. My point is that these mods do give an increase in power but doing these alone won't give you a ton of power right away. Someone with a 10th gen Corolla has dynoed their car after just installing a short ram intake, exhaust, and headers and they made about 10-15whp if I remember correctly. This was without a tune and from just those aftermarket parts alone, that is a good amount of gain and disproves those saying you'll lose power with those mods. Going back to the increase in power, an intake and exhaust will give you an increase in power but at a certain power range. For instance, cold air intakes may lower a car's lower end power and add a lot more to the higher end. Again, you need to understand how these systems work and have a realistic mindset on how much you can gain from these instead of just complaining that an intake doesn't give you a 100 hp right away.
Regarding your Civic, did you just install those parts and expect your car to beat a sports car just like that? Did you ever clean your intake to make sure it wasn't filled with dirt which made you lose power? Did you even have a 1.8L in that car or was it a 1.6L? Either way, you've got some wrong facts in your head and it's probably from the fact that you're Civic lost power due to your negligence of modifying your car. And I don't need to hang around any "rice groups" as I always do my own research and come to my own conclusions. I don't have to link another person's video to prove my point.
