Hello, I recently bought a 1998 audi a4 quattro with a 1.8t
I really want more engine performance out of it, but I don't know where to go now.
It already has,
Air intake
Forge DV
Borla muffler
Brand new sparkplugs and fresh oil,
What other upgrades could I do ?

a chip

A chip.

Bigger turbo.

A chip.

Check out the FAQ at the top of the B5 forum. Lots of useful info in there about chip tuning, turbo upgrades, and what's worth spending your money on vs. what isn't

https://www.audiforums.com/forum/b5-...%2A%2A-109459/

how far are you willing to travel down the rabbit hole? thats the real question.

CCA4 has a rabbit hole in his trunk.

Rabbits, rabbit holes, carrots, prostitutes, and a big bag of car parts.