2013 AUDI S7 Fuelpropulsion System Problems

I HEARD A POP SOUND WHEN ACCELERATING AND THE CHECK ENGINE LIGHT CAME ON AND I LOSS A LOT OF POWER. I CALLED THE AUDI DEALER AND THEY TOLD ME TO DRIVE IT IN. I LEFT IT WITH THEN AND THEY TOLD ME THEY COULDN'T REPLICATE THE ISSUE AFTER A COUPLE OF WEEKS. I WENT TO PICK IT UP AND THE PROBLEM STILL EXISTED. I WENT BACK AND GRABBED A SERVICE TECH AND WE DROVE IT AROUND THE BLOCK TOGETHER. HE ASKED THAT I ACCELERATE AT WHICH POINT WHITE SMOKE STARTED POURING OUT OF THE BACK. WE DROVE IT BACK. THEY DIAGNOSED IT LATER AS BEING A BLOWN TURBO. I HAD THE CAR TOWED TO A DIFFERENT SHOP TO REPLACE THE TURBOS AND THEY SAID THE ENGINE WAS DESTROYED AND ALL CYLINDERS WERE MARKED. I TOWED IT BACK TO AUDI AND THEY TOLD ME THAT BECAUSE IT HAD AFTERMARKET PARTS...