Diss = treat, mention, or speak to rudely.
air guitar = an imaginary guitar that one pretends to play; the action of pretending to play a imaginary guitar.
Cheetos = a brand of junk food, equivalent to potato chips in nutritive value.
Hook it up-- this could have several meanings, for which I would need more context; but basically, it means 'connect something with something else', I think.
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