I am about to swap my vw 2.0 engine with the 1.8t engine and a performance transmission. What would be the smartest part to add first, exhaust, headers, blow off valve, ect. It would be nice if you could list the parts in order from first to last that i should add to my gti Thanks!

you're doing an engine swap but don't know what "performance" parts to change? Ok... well here goes...
Chip or Re-mapped ECU.
Exhaust and Intakes would come next.
The blow-off valve is not a "performance" part... it just makes a noise that Rice Boys seem to find exciting.
(Ya know... loud noises, shiny things, etc)

lol headers on a 1.8t.

Do some research on the engine type, plus like Jedi mentioned above, if your planning on trying to put headers on a turbo car... do the research twice.

In this order, do the following.

1. Save up money for a year or two

2. Equip the 1.8t with a quaife differential

3. If VR6 GTI's have bigger brakes than the 2.0 GTI, do a stock VW big brake upgrade (with stainless steel brake lines and EBC brake pads)

4.Upgrade the rear swaybar with something from ABD or techtonics or whichever company has the best looking window sticker.

5. Upgrade to Bilstein HD or sport shocks/struts and H&R springs

6. You'll probably need VR6 wheels to fit over the brakes.

7. Equip your new wheels with Yokohama ES 100's

8. Wash your hands, throw out that VW performance catalog, and get ready for a whole new car.

You will straight up OWN all the other VW's in town, even if they have more horsepower. Your car will gain the respect of those who know things about VW's.

I have spoken.