how can i make my 04 gti 1.8t faster?

Your starting with 180HP... Like said prior to me, a Chip (Revo is the best IMO) is going to be the biggest noticable improvement you can make. Id start there, then go to a 2.5" or 3" DownPipe (Makes a HUGE difference in spool up times), then a CAI (Under the front bumper), then Exhaust to 2.5", and finally a K04 Turbo.. its a direct bolt on with no mods necc. After this setup you will be looking at having to get a "Big Turbo Kit" and replacing almost everything I just listed plus some.

Save your money for a Revo chip.

Nice car you have there. I am vw enthusiast myself. I drive an 01 gti vr6 =)

For the 1.8t the best bang for your buck would be a performance chip. This way you can increase the boost of the turbo and get yourself a nice increase in horsepower. Then of course there are the basic upgrades that dont hurt like the intake.

Then you can go in to lowering it, exhaust, flywheel, etc etc.

Certanly a performance chip upgrade is your best bet.

In addition, an intake system is an affordable easy mod that will give you a modest performance increase and also a noticeable improvement in engine sound. You will hear a nice growl from your engine when you are pulling hard and a nice wail when you are would up.

I think noise coming from under the hood is ten times more impressive than noise coming out of your tailpipe in smaller engines.

Exhaust mods on highly tuned engines will rarely result in power increases, only increased tacky noise.

Throw out all the seats and take it to the top of a hill.

You should be buying American, if you're an American.