<FONT face="Comic Sans MS">I can tell you from experience, and Cory will confirm, the added length has no effect on keeping the rear of the car any cleaner. That was the intent on the design, but actual use shows that they'd need to be an addition 2 feet long if they were to be effective.
Snake Oyl is a quality piece but adds drone to the nicer sounding exhaust it creates. If you don't like drone, spend the money on the Corsa.
If you ever plan on doing the Corsa, save your money on interim steps, wait till you're ready and then just do it.
If you're an experimenter, do the muffler cut up. An "H" crossover will help with the drone, (still slightly more than stock though) but in my experience produces less HP than the straight pipes of the Snake Oyl. You can't go back to stock if you don't like it unless you buy another stock assembly from a new Corsa owner though. Definite sound improvement over stock.
The dyno might show an HP improvement with all three, (stock cut up least, Snake Oyl second and Corsa best) but I question whether your butt will. It's all about sound......
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