On the attached picture of the engine on my 93 LS400, looking at the valve body (and there is a plastic cover which is not on my picture but it says TRAC Traction Control System) on front side of valve body is the TPS but what is the black round electronic device on the back side of valve body with a plug with about 6 or so wires going to it and what is its function? it is under the cruise control and throttle cables in the pictures. Thanks in advance.

 

One is the primary and the other is the secondary TPS sensor. If that is what you are talking about. Right close to the band clamp in the intake hose?

 

It's called the "Sub-Throttle Actuator". It's used for the Traction Control. Don't ask me how it works, it just does. LOL

P.S. Your coolant tank looks a little low.