I bought a used a4 s line 6spd with 83,000 miles on it when I drove it I was hooked very fast n it rides smooth. But the other day I was driving to work n when I pushed the gas to get the turbo to kick in I got some shudder from the engine. Then today my wife said the check engine light came on and the car wouldn't go over 40mph because it was breaking up . Now would the plugs n coil packs cause this I have a appointment at the dealer tomorrow morning to have it checked.

 

Reading the CEL should tell you, but what did the dealer say? I am betting coil packs.