Rs virginity lost!

[reg1988]

Hi all,
So just got my first audi!
A c5 rs6 saloon, always had petrol running through my veins so when the oppotunity came up to own one of my bucket list cars I had to take it.
Got a phew questions about the beast so any help would be much appreciated, so it has a cat back miltek and remap ( 520bhp old owner claimed) but in history it says at somepoint upgraded turbos. So am I right in thinking with miltek downpipes added would it be just a remap to stage 2 ? And what sort of power?
Also anti roll bars ? Any good makes ? Places to buy them?
Cheers Reg