I've had my Scion since August of 03 and the only thing that I've done to it was add LED lights under the seats and I got the TRD cold air intake, but that was around when I first bought the car. I want to know what is the first thing I should do to increase the power in my Xb. I know there are plenty of Scion gurus here so any suggestions would be appreciated.

get a super, or turocharger. that will give u the most boost than any other mod, if u have the money to get one.

header and muffler, or a cat back system and work from there

Lightweight Pulley
Header
Axle-back, cat-back, or full exhaust
Turbo or supercharger
Performance rebuild
Engine swap

This sounds like a GT4 tuneup. I definitely want to take the best route to increase overall power and performance. It sounds like the Mod knows what he's talkin about. Quick question though: What is a lightweight pulley? (I don't know too much about cars as you can tell).

The pulley is the thing your belt goes around when the engine is running. The one we change is the crank pulley which is the one that is connected to the Crank Shaft of your car. This pulley pulls a chain which moves the cams around and hence everything works. When you have lighter pulley the rotational mass of the ciruclar object is reduced greatly, hence letting it spin easier. As it spins easier your our engine dont have to make so much power to get it moving and the power goes to your tires not to spinning the pulley.

will a light weight pulley void your warentee? what is a good one to get?

The pulley is the thing your belt goes around when the engine is running. The one we change is the crank pulley which is the one that is connected to the Crank Shaft of your car. This pulley pulls a chain which moves the cams around and hence everything works. When you have lighter pulley the rotational mass of the ciruclar object is reduced greatly, hence letting it spin easier. As it spins easier your our engine dont have to make so much power to get it moving and the power goes to your tires not to spinning the pulley.

Everything is right except that the pulley pulls a chain to move the cams. The pulley drives the accessories like the power steering pump, AC compressor, and alternator. I have a Perrin pulley on my car so I'm putting a link to more information about it below but there are other brands to chose from.

http://www.perrinperformance.com/products/scion_xb/crank_pulley.htm

Thanks for the link. I have been doing a little research and from what I was finding on google it seems like everyone was offering the underdrive pulley, but I've heard positives and negatives about the crankshaft pulley and the underdrive pulley. I don't know which one is which, but based on PERRIN's description it seems like that is the one to go with because I want to avoid any type of engine problems down the line. Also it seems that everyone was raving about Unorthodox pulleys as well.

well to answer your question IMHO i would go intake first... its supposedly the least felt mod but man is it great to feel it...

here is my reasoning, if like me you want to do everything yourself, then the intake install is probably the easiest thing you can do. It adds a great sound and good feel for me, also this way you can acctually feel teh difference in all of the mods, and this is the one that i didnt want to miss feeling.

next ill do headers... as they are said to be the biggest performance gain, i am going with the mmw 4-2-1 headers as they give you some low end torque.

then exhaust, i choose exhuast for last because i wont be dissapointed if i dont feel the exhuast as much, but i know i will. also because of that guy who didnt feel the difference when he installed his headers, he had Intake and exhuast, probably just the axelback, i plan on going with something from precision muffler or the espiler cat back exhuast

so in short id say go for headers either way im sure you wont be dissapointed.

Judging from the size of the engine bay, are headers something that yuo could DIY? I just got a full set of sockets for my birthday a month ago and haven't found anything to use them on ;)