I've been thinking about ways to improve power on a vehicle, and it seems to boil down to air intake, exhaust output, efficiency of burn, internal friction, and aerodynamics. Decals alone add 20 hp, but that's for another thread
Most performance mods try to achieve more power by getting more air and fuel into the combustion chamber. I'm thinking about hi-flow filters, mandrel bent air intakes, superchargers, turbos, throttle body spacers, aftermarket fuel injectors and such.
What have you tried that works? And what do think is a bunch of crap?