Hi i am new to mods and i only know very little about them but not an expert.
I want to ask a few of some parts and what they do.
I have use "search" but did not see my answer.

1. What are spacers?
2. What are catbacks?
3. HFC?
4. Plenum?
What do they do?
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Also i am confuse about somethings.
These both cars uses stillen exhaust but sounds really different.
Sounds i want:
1. 2. Sounds i dont want:
3. 4.
I am trying to get the sound like #1, #2 with a stillen exhaust but when i heard a different sound of a stillen exhaust from #3, #4. makes me not want to get it. Which of these sound of the exhaust is correct? Because i do not want to waste money on getting the wrong exhaust and could be a screw up.

So like #2 video says he got stillen exhaust and an injen cai. If i get the same thing will it sound like that?

I dont like the sound when the exhaust go poot poot poot.

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Which is the best intake that makes the engine louder?
I looked into nismo, stillen, injen but not sure which one to get. They all sound the same to me when i looked it up on youtube but can't figure out which one makes the engine louder.
(i love the sound of the infiniti engine)

1. spacers= a device (usually made of metal) to create more space between two objects. we have one for the plenum, rims, and throttle body.

2. exhaust systemt start from the cats and goes all the way back to the muffler.
3. HFC = high flow catalytic converters-some replace stock cats with test pipes.
4. upper and lower plenums make up out intake manifold

for exhaust system meaning starting from the engine?

Our exhaust runs as follows:

engine -> headers -> catalytic converters -> Y-pipe -> mid-pipe -> muffler -> exhaust tips

high-flow catalytic converters (HFCs) are less restrictive, allowing exiting exhaust gas to flow better, and in turn, increase horsepower. This comes at the expense of some increased noise.

Check out this site as a starting point for alot of your questions:

http://www.350z-tech.com/zwiki/Infiniti_G35