So i have had my audi a4 2001 turbo for a month now, but recently it has devleloped this noise from the engine bay and i have no idea what is causing it.
It can only be heard under heavy heavy load, and it fades in and out, like some part is rubbing during the accleration. And once it gets to 3rd gear it stops. I am not familiar with audi, so i am not sure if this could be bad motor mounts, exhaust loose steering components ect.
Know issues with the car are that the cat is bad, i am replacing that this up coming week, and there is an oil leak from the bottom of the engine, but it is to cold for me to get it up to look at it. Also before this happened, the car got a flat and i traded it out for the full size spare, same size as the other just a different tread and width.
This is really starting to bug me as i just bought the car and i like it when my car runs smoothly, so any help is greatly appreciated! thanks for looking!

 

i meant heavy load, not heavy heavy lol i am not a nascar driver

 

just an FYI, cars with AWD (quattro) should always have the same tread patterns. if you have a quattro u might wanna look at matching the tires.