If your car is new enough [and I think yours is], the computer controls the timing anyways, and you won't be able to screw it up too much. As for the hesitation you described, that's known as "cam hunting." When you change cam timing, you change it's effective RPM range, so if you advance it, the power curve is going to be moved up the RPM band a bit, so you're tettering on the edge of it's range before you make enough RPM for the cam to start doing exactly what it's supposed to be doing: making power. This isn't all bad if you drive in higher RPMs a lot, learn to deal with it, and/or the gains outweigh the drawbacks, otherwise it's just an annoying hesitation.