alot of ppl mistaken that the ivtec is for performance or racing engine design. the ivtec we seen on the road are valve timing control, which continuous changing the cam timing according to different engine rpm and it cant be feel the crossover of the cam timing change. The original Vtec is those cam lifting engine such as B series , K series and H series engine which is totally a performance NA engine, that why the word of vtec kick in come from when the engine rev until certain high rpm and the cam profile changed that you will feel the power from the engine also different sound from the engine as well.... anyway, ivtec and idsi both are design for fuel economic but ivtec will focus more on engine response...