How much power do engine mods yield?

Turbo mufflers sound nice, but turbo-chargers sound better... much better piece to put in the exhaust line IMO...
[ame="https://www.youtube.com/watch?v=QTutTfYHVI8"]Turbo 225 Sound Bite Engine bay and Exhaust - YouTube[/ame]

[ame="https://www.youtube.com/watch?v=HElZ4DB49k0"]Turbo Slant Six Dyno Pull HybridWorks - YouTube[/ame]