No...most performance cars have a LSD in them which does help a lot with cornering. Essentially it allows for power distribution between the drive weels when cornering, which can equal much better handling on the road and esp on a track. Even the new Si has one actually...
As far as LSDs and the 7th gen 6MT goes...from what a few guys have been saying on V6P is that the 2004 TL's is a direct bolt on to our 6MT transmissions, as it's basically the same transmission with slightly different ratios. Keep in mind that in a FF car the LSD/differential is inside the tranny...so to be able to install one the tranny must be dropped/removed, opened, and worked on.
I think they were saying the parts alone would be around $1000-1400, not to mention a fair number of hours to be able to get it all done. Princess might be able to get a better estimate on labour time as iirc her Prince does a lot of tranny work for Honda (but it might be on ATs and not MTs)...
All in all adding a LSD is something I might be considering once my warranty is gone...however at that point in time I'll probably be thinking of a new car in the next few years following...so dropping $2000 or more is something I might not be willing to do at that time.
