i have an 03 xterra SE Supercharged and was wondering what is the cheapest way to boost my horsepower and is there anyway i can get more force out of my supercharger without it risking blowing or harming any parts or my engine

high flow air filter, pulley, exhaust for starters

Exactly what Dustin says.

X3 with that

does anyone know someone that's had installed a new pully into the supercharger and it being 100 good and it not having any negative effect of the original performance... And last thing does anyone have a clue how much more horsepower u can gain after a new pulley? Thanks a lot =]

Dyno it. That's the only way you'll be able to see exact numbers from a new pulley.

yea but im trying to figure wether intake or supercharger pulley which gets me most bang for my buck

i would figure a pulley would have a bigger performance booster fro the buck. Add an intake and exhaust and you should be lightin those tires up. Im sure the motor can handle the extra HP without any issues.

I bet it would ripp and still be a reliable DD.

i would love to find a SC X

A SC'd 2nd gen would be the answer.

The factory was very conservative with the 1st gens and the SC doesn't add a whole lot. Add in the problematic KS and you're looking at a something that's a lot of trouble for the gains given.

pulley, intake, catback exhaust and headers would be nice, 4x4parts sells the smaller s/c pulleys and the headers.

What about tranny issues? Nissan did de-tune the Xterra when equipped with 5spd trans

The "safest" upgrade would be to swap out the air-filter. At that point you doing nothing "permanent" to the truck.
As far as the pulley, exhaust, etc. are concerned you are pushing past the factory threshold. Not far, but...