Quote: "anything that modifies the intake / output of a care SEVERELY limits its life, not to mention voids warranty"
Well it would put more stress on the engine, but hopefully people who tune the power in their vehicles do so with supporting mods to handle it. For instance, my grand prix had stonger pistons than a normal one would have. But most ppl who supe up their car usually is way past a warranty anyway.
Quote: "I don't understand Mr 400BHP 6 litre, when a 2 litre twin turbocharged engine can have more BHP. Surely the only correct answer is a 6 litre twin turbocharged engine?"
Mine outputs 400hp with only 4.2L

But why do ppl use bigger engines in production cars? I bet i get better gas mileage than someone who manages 400hp out of a 2L 4 banger, which is only 24mpg highway.
Basically, smaller engines are capable of high output but you have to consider emissions and street regulations.
Speaking of gas prices, I just saw it for $7.50 a gallon, but that was for 110 octane. I was kind of surprised to see that at the pump.
Quote: "is there a way to make it autimatic control over the fuel injection? so more presured air will enter, and automaticly the fuel injection will be lower?"
Well you would actually increase the fuel if you're forcing more air, there's a certain percentage mixture you want to maintain, and I couldn't tell you what that should be. Most of that stuff is regulated through computers these days. Did a quick google search and it says the mixture is 14.7:1. Too little air, you're burning rich, too much then the fuel burns lean. With the wrong ratio you could damage the engine. The O2 sensor detects this and tells the engine whether it needs more fuel or air to meet the preferred ratio.
I couldn't really say if your car would just automatically adjust the fuel when it detects the increased air you're forcing or what. I know a little about cars but not enough. My guess is you'd probably need the ECU reprogrammed.
I feel like I'm rambling. Long story short, more air equals more fuel, not less. DigDug would be the guy to ask about cars.
"Only the educated are free" ~Epictetus
"Imagination is more important than knowledge..." ~Einstein