I typically log the following, which is a mild departure from the parameters suggested by Cobb in their AccessTUNER tuning guide:
RPM (RPM)
Accel Ped. Pos
TPS Act
Req. Boost Abs. (PSI)
Boost Mean Abs (PSI)
Boost (PSI)
WGDC Bank 1
Charge Air Temp
Timing Cyl. 1
Timing Cyl. 2
Timing Cyl. 3
Timing Cyl. 4
Timing Cyl. 5
Timing Cyl. 6
Lambda (Bank1) (AFR)
Lambda (Bank2) (AFR)
STFT (Bank 1)
STFT (Bank 2)
Torque Limit Active
Fuel Mode
The reason I don't log timing correction is that I can deduce that from the timing in 1-6 as it is. It's imperative you log all cylinders, because a single cylinder pulling timing means next to nothing, but seeing 3+ cylinders with reduced timing is an issue, one that might be missed logging just 1 or 6.
Reference, Cobb's tuning guide:
http://www.cobbtuning.com/v/vspfiles...FinalAlpha.pdf