actually an rs6 ownes an m3 all the way even from a roll we haved raced plenty of m3s with a astock rs6 and went by them 1-2 carlengths and still pulling. the video m5.com posted was a modded m3 despite what they said. plus i am assuming that the auto forester and the auo wrx are the same quick. if u put a chip and exhaust like i did in the rs6 its pretty hard to modd and sti to stay up with it of course u can do it like nitrous or change the turbos but then u have to empty youre pocket
and dead pool if anything porche took the rs6 engine because audi had the 4.2 V8 since i think 1999. and when you are starting from a roll wieght doesnt make that much difference from a roll spcially at high speeds.