I don't think it would increase NVH, though I am sure piping diameter has an effect on this especially when you have different diameters. I once was going to put on the Megan Y pipe, but ended up getting an OEM one as I was worried it would effect "emissions". Sounds very stupid but I read conflicting things on it.

The worst NVH I ever had from an exhaust was from the Q50 OEM helmholtz axle back, it was bad, I have zero clue how people like it. Did not even sound that good, only when you rev'd it did. But it completely ruined the quiet cabin with drone, resonance and vibration. The Tanabe on my G, is awesome wish I could said the same for the Q lol.