go with the engine balancing, it increases your redline. even if the tach doesnt show it , my silvia varietta s15 can rev all the way to the top of the 8000 rpm tach, usefull when trying to sustain drifts through a long corner. this is the only permanent power upgrade i try to use in most cases, for tuning purposes. as far as the NA/Turbo debate, this silvia has been my first NA tune drifter, and I kinda like it. Im not about to tell you the differences between the two cause i couldnt tell you. Just purchase a few of each, engine chip, and all the exhausts and you can pretty much play around with combinations to get the car to have exactly how much power you feel comfortable with.