Having an xpipe or an h pipe with a turbo system won't mess anything up mechanically at all. Is it a detriment to performance? Well, maybe slightly but in all honesty only dyno testing would prove one way or the other. My comment about them not being ideal for turbo applications stands however. Like I said before x and h pipes are used to scavenge exhaust gasses to help evacuate better/quick in NA application where there is no force induction - nothing to help push the exhaust gasses out. The goal with exhaust is to get it out as fast as possible, with NA that is with x pipes and h pipes and with turbos, that is a straight through exhaust.