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That's one argument they have that makes sense.  For any type of racing that involves turns, the responsiveness of an NA engine is beneficial.  You want as direct of a response as possible from when you modulate the throttle to when the engine reacts.  Turbos, superchargers, and NOS all clutter and delay that response. You can make turbos, s/c etc. perform very well, and they can be a blast to drive in teir own right, but from a strictly performance standpoint, the directness and linearity of a 5 liter V8 versus a turbo'd to hell, NOS'ed 1.5 liter four cyl will make it a better choice.  It's also simpler, has lower cylinder pressure/temp and is less prone to blowing up.  And if you're doing things the irght way and designing a car around an engine, the weight/size increase isn't a big deal.  
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