HKS Type-S for a R34 GT-T plumbs back under the cooler to the original pipes. Thats why I want one, stuff going over the engine bay. You can buy a HKS upgrade kit for the rest of the pipes worth about $800-$900.
Check it out for yourself at: -
http://www.pbase.com/franks/07dec02_fmic_i..._install&page=1
(Thanks to Franks for that one, legend!)
As far as I know on the R33's they flow over the engine bay.