Think of it like this.
Get a straw and blow in it. Its easyer for you to blow out the whole straw since its so small that all the air you put it in feels it up quickly and it goes out faster.
Now take a paper towel tube and blow in it. its harder to blow fast due to having such a large space to fill and the air to go out.
Same concept. You have a smaller pipe(2 inch) the air can move quickly out of it sine the air is filling it up faster. Instead of a big pipe (3inch).
Instead of moving in the big pipe the gas just kinda lingers around when it gets farther from the engine.
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Driving definitions: Understeer is when you hit the wall with the front of the car and Oversteer is when you hit the wall with the rear of the car. Horsepower is how fast you hit the wall and Torque is how far you take the wall with you.