If you want your 172 to sound like its got an induction kit and cant afford one, try removing the cold air (front of car) feed pipe from the air box. The air is still being filtered, so no harm to the engine etc. But it makes a lovely induction roar that sounds like youve got an induction kit! cool, huh?! or am i just sad? Im thinking of moving the air feed from the wheel arch to the front also for dual ram-air effect! +200bhp dontcha know!!