As MD says, both have been discussed quite a bit.

The Coles Notes version:

The shark injector is only for the 3.0 six cylinder, and claims 2.5% increase at 6000 rpm. They claim about a 1% increase at normal driving rpm. You would never notice either increase in the real world.

The Sprint Booster doesn't claim to increase power, although there has been some confusion about that from some posters. It changes the mapping of the accelerator pedal to give a different response, which some drivers like.

If you have a 3.0 and want to increase power, the only real way to do it is with a supercharger kit, and that costs $$.

__________________
2007 X3 3.0si, 6 MT, Premium, White

Retired:
2008 535i, 6 MT, M Sport, Premium, Space Grey
2003 X5 3.0 Steptronic, Premium, Titanium Silver
2002 325xi 5 MT, Steel Grey
2004 Z4 3.0 Premium, Sport, SMG, Maldives Blue