Or could it be time to change your exhaust. Speed bumps are a complete ball ache not really applicable to you as your in a major city but I just have to detour certain routes and I am on stock suspension. I had full unresonated cobra exhaust cheap and cheerful sounded good but I went for the single exit as tomie don't offer a dual option which to be fair looks in my opinion crap how ever style is subjective but I brought it for the sound not the looks. In the US they have loads of tomie/single exit exhaust uk how ever not so many and I unfortunately due to work got chance to go to a meet to hear one but I went from not ideal and would never do it normally YouTube videos and it's renowned to be loudest exhaust and wow my god it is loud!!! the tomie is absolutely awesome yes it p**es some folks off even more when I get the pops and bang map but long as your not gunning it every where stay below 3000 rpm but personally I don't care. My mate has it on his r35 again still looks stupid but sounds even better. I certainly woulnt recommend it if you like listening to anything whilst driving bar an exhaust, talking any one or don't like unwanted attention.Want to do any track days as it's to loud that does suck but I daily drive mine and I have another z for the track now I did have berk test pipes but with the tomie had to take them off. as that was way to loud.