first mod i did was take the middle silencer off, at first i thought it would be pointless, but it knocked me back, takes a few weeks for the sound to settle, but it kept me smiling for ages, it will give you a touch more bass, nothing OTT, and will give you a satisfying high pitched note on high revs.
trust me, give it a go and see for yourself.
also, i have a video somewhere of my Z, got my lil sis to rev it the day i took the middlebox off & put a popcharger in, let me know if it will help and ill send it to you.
Can you post it? I'd be quite interested in hearing it!