Have I got a story for you...
In the period of 3 days I have tried:
(1) Redline MTL
(2) Royal Purple SyncroMax
(3) PENTOSIN "Lifetime Oil MTF-LT-2" (BMW OEM)
In my Maxima, I loved Redline MTL. My BMW doesn't like it very much. The shifts lost their nice "snick" into gear. It felt like I was hitting the syncro just as it went into gear. I hated shifting the car.
About 80% better than Redline. But the best was...
PENTOSIN "Lifetime Oil MTF-LT-2" This is designed for ZF manual transmissions. The shifting is now back to awesome. I purchased it from bimmerspecialist.com for $20 per liter in 2007, but I don't see it on their site now.
Link to US site that sells it: http://www.rmeuropean.com/Part-Numbe..._9BA48850.aspx
You should also change your diff oil. Any synthetic 75w90 will do. I used Redline 75w90.