Interesting comment. What system(s) have you researched and what did you end up installing?
On a $/kW (or $/HP) uplift basis alone, ie ignoring all other benefits (eg build quality, support, ease of installation and removal), I found the NM Engineering Power Module on its own in terms of bang for buck.
I've now run a full tank of 98RON (AKI 94) fuel with the device on LOW setting and a full tank of 102RON (AKI 98) fuel with the device on HIGH setting. The impact on performance, by feel alone, is profound. Next will be dyno to confirm.