Tsudo Catback

axelback replaces a muffler, keeping the stock midpipe, s pipe, etc. and catalytic converter. They are generally quieter and the exhaust pipe is stock, it will not increase much HP. However, catback exhaust systems replace the entire system, removing the secondary catalytic converter. they produce much more than horses would axleback because the catalytic converter is restrictive and lower HP, so removing that would increase the flow of exhaust gases from the engine.

Here's an analogy: in a glass of water, try to make bubbles through a straw, coffee-stirrer. its quite difficult, but try to blow bubbles take a normal size glass straw ... is much easier. see what I mean? The catback system is like the biggest straw allows air flow more freely and thus puts more power.

There are many catback / axleback exhaust systems out there, some brands that I know are:

1) Tanabe
2) greedy
3) megan
4) tsudo
5) HKS

I know there are many more other over there, go to a forum SCION xB, and ask around. People will help you a lot more than we can here.

Depends on what they are talking about the axle.

If the front axle, it includes everything, including the cat.

If the rear axle is pretty much just a muffler.

As for what works .... either would work.

But none of these will do something unique for your car.

Is a Scion xB. At most, you might see 1 or 2 extra PVT. And no, it will not be enough to notice. It might actually make the car slower, because it's too high an update for the vehicle you have.

simply replacing the exhaust will not do much for your system or the other ... if you have the money, go with catback exhaust, it sounds better and be more effective than simply replacing the muffler with axleback ...
Of course, if money is not a big problem, just replace the header too while you're ...
Of course, if nothing ing money for you, than go buy a porshe and do need to upgrade your exhaust system in the first place

catback will generally be longer, which means more power. axleback is shorter, therefore less power, but its cheaper. and you do too much HP out of it, but its better for your engine and you'll get something out of it.