quick question...i wanna install an LSD in my Si tranny (s4)...but i'm trying to figure out which LSD would actually install and work...

i heard that all bseries trannies are almost identical so that an oem ITR/CTR lsd would work with mine...but after calling up some local tuner shops, they told me that the ITR/CTR lsd wouldn't work with my tranny cuz of the different final drive...and that i'd need to get an LS/GS lsd...

so, can someone please tell me the final verdict on all this?? if i got the final drive from an ITR or GSR, would i be able to run the oem ITR LSD? or, would it be better to just get an LS/GS lsd? or, even better, are the local tuner shops in my area feeding me BS?

lemme know! thanx!!