Not necessarily more power, but more along the lines of ryousuke's weight saving.
Saving weight not only helps acceleration, but all aspects of the car's handling, braking, etc. Especially if it's unsprung weight (I.E. lightweight rims/tires). Also, lowering the center of gravity helps a lot, along with corner weighting the car (to acheive a 50/50 weight distrobution not only front/rear but also left/right). I think he's got a long way to go before he needs more power. Keep in mind, he's got a race engine under the hood.
As for competing with Bunta, Takumi's got a long way to go before he can even hope to compete. (driving style/tecnique wise, not car wise)