I've just bought a coolcharge II ic from Pettit, and I think the piping it comes with is a silicone hose kit. I'd prefer having some other kind of aftermarket piping, like aluminium ones, but I'm not sure if some piping that is supposed to fit with the stock IC will do the same with my new pettit unit... would they fit??

 

You would be better off asking Pettit. I know the old style Pettit Coolcharge II cannot use something like the Greddy pipe kit for the stock IC.

 

Most of the Pettit items are for use with the stock plumbing, so if you use a Greddy elbow then you'll have to find the filler pieces to make up the difference.