Want more power?  Want better milage?  Want a cool exhaust tone?  Want all three?  Through proper exhaust setup, it's very simple.

If you've got a stock L24, and want to get started on the road toward Z-car performance, there's no better starting point than the exhaust.  2.25" inch pipe will work very well for an L24, but 2.5" is a little better in my experience.  This is particularly true if you want high RPM power, or if further engine modifications are in the works. 

The Z-car engines have an annoying boom near 2000 and 4000 RPM.  A good discussion of this can be found on the IZCC website.  The short version is that the boom can be reduced with a resonator (a glass pack muffler for all practical purposes) placed near the transmission.  Another option is to place a collector of the two headpipes about two feet downstream of the header collector.  This cuts the resonance without sacrificing exhaust flow like the glasspack. 

Here's a few pictures of the setup I run on my street-driven L28/E88.

  
    This is the overall system... 
   
    Closeup of the Y-pipe... 
 
    Ooh, metallic road debris - look out!