throttle body spacers and creaking

[smugpuff]

Hi All,
I'm new to this forum, and I have to say I have been very impressed so far.
I am considering buying a Helix Power Tower for my '03 ZX5 and was hoping someone could give me some feedback as to whether they are worth the money or am I better off investing it into something else. I already have a k&N in the box and will be making a CAI mod shortly.
Also, I have nearly 20k on the clock and am getting a creaking noise from the rear whenever I make a r/h turn. Any thoughts as to what the *^@$ that might be? Thanx in Advance.