Dyna CDI ignitions - any good?

I found the following CDI ignition on ebay and it claims up to 9 horsepower increase, which isn't a lot for $550

Would you need an exhaust, airbox and possibly flatsides to those gains, but if you had exhaust, airbox, flatsides would you need this? And where would I put it?

http://cgi.ebay.com/ebaymotors/ws/eBayISAPI.dll?ViewItem&item=380066544773&sspagename=STRK%3AMEWAX%3AIT&viewitem=

........(a) Would you need an exhaust, airbox and possibly flatsides to those gains, (b) but if you had exhaust, airbox, flatsides would you need this? And where would I put it?.....

(a) - Yes. Add hi-comp pistons, and hi-performance camshafts as well.

(b) - If you already had the zorst, airbox and flatties, then its just hi-comp pistons and cams, if you want the *maximum* benefit of the Dyna.

Where do you put it ? Wherever it can fit - generally they get mounted near the battery box/underseat area. The actual physical size of the ignition module is not that big - not much bigger than a pack of ciggies really.....they can be squeezed in just about anywhere, as long as they are not located to close to heat sources (above the motor or near the zorst).