The most recent issue of Grassroots Motorsports has a very informative article about aftermarket cat-back exhaust systems. They took an older VW Jetta and dyno tested 8 different systems. Some were pre-fab kits specific to that car, others were crush-bent w/universal mufflers. As it turns out, the best numbers were attained by the cheaper systems! For instance, 2.25in pipe with a $30 Magnaflow muffler (total installed of $125) had a 6 hp gain at the wheels- the 3rd best of the group! One of the poorer showings was the bosal system, even though it was one of the most expensive. Finally some cold, hard facts on this long debated issue!

 

I never said it was DIRECTLY applicable. However, the concept of the internal combustion engine only has so many variants- therefore, some things are still good for general reference. No offense Pseudo, you really know your stuff, but you're always such a naysayer. Thats not a slam, but c'mon, lighten up!

 

Well I'm sure custom exhaust systems may be just as efficient as other tuned systems. The only benifit i see from using a system made specifically for the car is that it was tuned for max gains and tested. Can't say every company does this. But if you are short on cash, I would say a custom exhaust system wouldn't be a bad alternative. But the only way to really know is to have the systems tested because it varies on different cars.