If you remove you seat and look at the top of the carb, there is a square cover with 4 screws. Remove them and pull the spring and the slide out. The needle is inside the plastic slide, using a phillip screwdriver make a 1/4 turn to the left on the locking tab inside the slide and it will unlock it and come out. Just be careful not to drop or lose the small spring and washer with the needle. The factory needle has 5 different notches on it for adjustments.
The air/fuel mixture is on bottom of the carb close to the intake. If you do try to adjust it, just remember where you started and only make 1/4 turns or less at a time.
I'm suprised that the direction's that came with the pipe didn't explain the adjustments on the carb for fine tuning.