its hard to varify what the noise is exactly without hearing the noise coz some noises sound quite similar, but u say u can make it worse when selecting a gear but the noise goes away when u engage the clutch abit in gear? Possibly an internal gearbox drama, mainshaft bearing/s, counter shaft bearing/s something like that, but again unless i know whats actually happening and when, with what noises etc its hard to tell u, ur best bet is to talk to someone in person(ie a mechanic or gearbox place) and see what they say. U could try talking to boosteds15 of www.boostcruising.com he has an s15 which has had afew gearboxes replaced. maybe u have the same drama