The elusive and to often "live with it" attitude that the early Z31 car owners have had to deal with may now be SOLVED. I'm referring to the cold start performance of the 1984 and 1985 300ZX when the car would stumble, buck and/or hesitate do to a "lean mixture" condition until the engine would warm up.
Recommendations over the YEARS from very knowledgeable people range from changing ECU's from other vehicle years to changing multiple sensors from the exhaust up to the CHTS. The FIX is simple, which is why it was probably overlooked all these years. The short version... WD40 in the EGR Valve -Solenoid. It WORKED on my 1985 300ZX -GLL.
For the entire story and the thought process behind this fix go to the original link (from the Connecticut Z Car Club {CTZCC.com}) and is attached:

CTZCC.COM ? View topic - Cold Engine/Transmission "Bucks" until warmed up