Overall Issue

Originally, the 2000 model year Audi S4 came out with an original design rubber throttle body boot. This was then replaced with a revised part in early 2001, that seemed to be slightly modified to address the tearing issue that Audi was seeing on warranty claims on this specific part. Besides just replacing this part by using another factory part, a few tuners have come out with alternatives. The nice folks at Advanced Motorsport Solutions (AMS) came out with kelvar tape enhanced throttle body boot that is currently used by a number of Audi S4 owners, including the author of this User Review. This alternative replaces the stock clamps with high quality clamps as well as wraps the throttle body itself in reinforced Kevlar tape.

Audi Performance & Racing (APR) sought another approach to this issue. APR decided to totally remove the rubber portion of this throttle body boot and replace it with a bi-shaped part (as seen in the pictures attached) that totally removes the rubber components. APR calls this part the APR Bi-Pipe.

Where does it go? 

The APR Bi-pipe replaces the stock throttle body boot and associated piping that goes from the throttle body boot to the intercooler. 

Advantages 

The APR Bi-Pipe removes the need to change the throttle body boot. 

Disadvantages 

Whenever you modify your car and remove a part that is relatively easy to replace, and replace it with a part that strengthens that system you put yourself at risk of moving the easily accessible repair of the stock part, with a more elaborate repair somewhere else in the car. 

Performance Gains 

It is anticipated that there are nominal gains to the addition of the APR Bi-Pipe. What actually happens is that the Bi-Pipe prevents a boost loss that sometimes accompanies the use of the stock throttle body boot in a chipped S4. 

Availability/Where to purchase 

The APR Bi-Pipe can be purchased from any bonafide APR distributor across the US. APR-Europe also sells the product directly to the European market. Cost is approximately $350US. 

Ease of Installation 

The Bi-Pipe takes approximately 45-60 minutes to install with a 13mm socket wrench and a medium sized standard screwdriver. 

Overall Impression 

The Audi Performance and Racing Bi-Pipe is a valuable modification if you are looking to get maximum power from your Audi S4.