Hello everyone, my sister recently bought and Audi A4 2003 Quattro and everything was fine till recently. The car got a check engine light on, and if you try to accelerate a bit hard the whole car vibrates and the RPMs seems to try to get up but it's hard. If you press it harder the RPMs will jump up and not go up smoothly. I revved it once on neutral and there was a lot of smoke coming out the exhaust. I don't think the turbo is bad but I think there's something wrong with it. Anyone has any idea what's up with the car? Thanks