My car sounds like a freaking police siren so this turbo needs to get fixed. I was thinking of getting a Ko4 instead of the Ko3. but will i need ti chipped etc? what other parts besides the turbo will I need to replace? Thanks

 

There's some more stuff in that thread and some of the other FAQs that's really helpful. Copy pasted the main part from that link.

https://www.audiforums.com/forum/b5-models-69/1-8t-turbo-upgrade-information-93439/

K04

The k04's lag is pretty much non-existant but you'll max out around 250hp and you won't be able to hold that power until redline. You will not have to change anything else except for the oil lines and software. For the aggressive files, you will need bigger injectors, an adjustable FPR, FMIC, and tuning. Some form of an aftermarket exhaust is also highly recommended.