I have one of the first Stillen Y-pipes that was made. I recently developed an exhaust leak. The leak is right where the 2 tubes that run into the collector first meet and are stacked on top of each other. I had dime sized holes in both the upper and lower tubes facing each other. I took the Y-pipe to an exhaust shop to get it checked out.

The cause of the problem is a typical Stillen screw-up(no they can't do anything right). They placed the 2 tubes next to each other, but they aren't welded together. As the tubes resonate over time, they are inconstant contact with each other and eventually break holes in the tubing. Fortunately for a mere $10 I was able to get the holes welded up. They also welded the tubes together to prevent this from happening again.

Anyone purchasing a Stillen Y-pipe or with one on there car, I would strongly recommend taking it to an exhaust shop and having a sean welded between the tubes. This will prevent any problems in the future.