In an ICE car the part of the tailpipe which is wider (which I believe is also were the catalytic converter is) is tuned to change the engine noise (mostly to reduce it, but it can also be tuned to make it “purr” rather than “roar”, like in sports cars)

Cut that out and the car becomes much louder (and if it’s not diesel, I believe it’s with the kind engine sound one associates with muscle cars).

If I remember it correctly, the second normal at lower IQs was due to environmental factors during growing up that caused some people to have a lower level of intelligence that they would otherwise have.

I actually went and investigated this at some point out of curiosity and came across a paper showing that intelligence is not a normal distribution but a sum of TWO normal distributions, the second one much smaller than the first and slightly offset (towards the lower values if I remember it correctly).

That being so, for the distribution of intelligence in humans the median is not the same as the mean (which is what’s commonly meant by “average”) so it’s slightly incorrect to say that half of people are below average intelligence.