I'm so high I need parachutes
Lil Wayne is comparing the level of his high (due to use of drugs).
To the altitude you are at when you jump out of a plane and use a parachute to come down at a slower rate.
When you start to lose your high it is called coming down, so Wayne got so high and now is coming down from this massive high. Since Wayne is coming down from this crazy high, something to ease it would help-which parachutes do when you jump from planes.
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