first time I heard about downpipes was a decade or so ago when I lived next to a motorshop that prep rally cars on the side. On their turbo rally cars, the down pipe was the whole exhaust system - basically a large pipe that connects to the turbo and long enough to clear the engine bay - maybe about 3 feet in lenght. That's it. Really loud but awesome. Purpose is to free up the turbo from any restriction as turbo's would spool up faster that way, decreasing lag time. I haven't seen a down pipe for an A4 but for other import tuners, it appears like a larger piping to connected to the rest of the exhaust sytem - which I think of like headers for a turbo. I could see the down pipe as beneficial for larger turbos that have a tendency to lag (due to larger size and more inertia to spin required), but with a stock turbo, the stock piping is probably good enough. Let's see what others say - I don't have a turbo car.

When I think downpipe, I think of a pipe that connects to the<br>turbo itself. On the A4, the cat is connected to the turbo. There<br>is no real downpipe. Are you thinking of installing one between<br>the turbo and the cat? Or are you thinking about a pipe after<br>the cat?