Where is the turbo and the blow off valve in a '99 Audi A4 1.8T?

It is on the exhauist manifold. I suggest you get a manual on your car from AUTOBOOKSONLINE.COM and it will acquaint you wiht all of the things under the hood. Our cars don't have BOV's! They have By Pass Valve's so the excess air get sent back to the airbox and get metered. And it's located on a hose which goes from the air box down to the turbo. It's also got a little 1/8" hose which connects to the top of it. It's basically located behind and a little below the Passenger Side headlamp. Easiest way to get to it is from the bottom of the car with the belly pan cover take off.