1 - There are Turbo now available for as low as 50cc mopeds as well
2 - Not only TurboChargers but Super Chargers are also avaiable.
3 - EFI systems, bolt on fit to RP are also avaialble.
5 - NOS injection kits of various stages also available.
Cost would depend upon your will.. a simple turbo charger Price + Installation might cost you some where around $1500 or more now tell are you still interested
For only show off electric blowers are also avaialble which do not give any 'REAL' boost but look cool and are easily bought from china websites like Ali Express..