I have owned my 2011 MS3 for roughly a year now, noticed a creaking noise coming from near the bottom of my firewall every time I apply throttle (even really light throttle) especially at low speeds, somewhat sounds like metal being stressed, the more I step in the more painful the creaking gets.
It's not really loud, I can drown it easily with music slightly turned up, it also disappears after I get into throttle and stay there, but it is still getting on my nerves.
Really wanted to fix it, but can't seem to find the actual cause. Doing research, most just suggested motor mounts were going bad, which I don't think is my case.
The problem doesn't seem to affect driving and my MS3 makes a lot of noises already, but it's just this one that seems to hurt(the odd feeling of pain ).
I would crawl underneath to both footwells and push with your hands underneath anything there to see if anything would creak. You can remove the radio and glove box to see anything there would do the same thing. I wouldn't think motor mounts either.