Most cost effective HP+ modifications?

[ProjectM96]

I looked at all the power adding mods available for the Boxster and added the HP claims all together. I excluded superchargers and turbochargers.

I got $90 per HP. Parts include performance intake, low temp thermostat, underdrive pulley, headers with sport cats, secondary bypass pipes, performance muffler, ECU upgrade, Pedro's Plenum upgrade, added 2HP for desnorkel and iridium sparkplugs.

I say most cost effective mods are ECU upgrade combined with performance intake and bypass pipes. $1700 for 20-25HP according to claims. That is about $78 per HP.