Teleflex 5600 throttle creep, parts missing?

[Ontariochaparral]

I have the four stick throttle and shift control in my V350. Driving slow is no issue but @ 40 kph the throttles slowing come down. It's hard to hold the for extended runs.

I started looking at the parts diagram and noticed I have no friction springs and set screws (pictures attached). I started reading and it seems these are optional.

Will these solve or at least mitigate the problem?

 

[Bt Doctur]

adjusting the friction control is better, the shift detents would not hold it in place

 

[Ontariochaparral]

The throttle cables are attached to the black arms. The friction adjustment spring and set screw are missing. I am going to pick up a 5/16— 24 Set screw and a spring. It looks like that will do the trick.