Hi Stephen here,
We do not have any sort of bad suspension in our 2004 but did have squeaking as well. In our case it was due to the small rubbers on the side supporting the roof board. I just used a very small amount of WD-40 and the rubbers and the problem was solved. White lithium grease is very useful for all sorts of squeaks rubbing and corrosion I keep a small tube in the bus I bought this as a bicycle repair shop or can be purchased at Auto material shops.
Good luck!