What is the difference between a standard and a -31 actuator?

I appear to have a standard actuator on my car now but it was wound right in and has side to side play.

Is it worth upgrading to a collins -31 actuator whats the benefits?

 

a worthwhile upgrade. its stronger spring allows the boost to be more stable, something of an issue with a tired old unit. -31 equates to a minimum preload of about 10psi irc. mine has been much better since swapping my actuator to a -31.

 

I have an as new garrett -31 for sale bought from burtons ,prob been on the car for a week then took off

 

How much delivered? i can get a brand new collins one for 70 delivered