I'm glad you found the problem. When I found the problem with the one side and looked at it closely I decided that I would replace both of them because they are the some age and I figured that the other one would start leaking air very soon. When I got is out I pulled on it and found lots of dry weather cracks in it so it wouldn't have been long until it broke also. When you get the part in at the dealer check it over carefully as one of the new parts I got was defective. The part came apart in my hands when I tried to install it. The two pieces that hold the rubber together weren't glued together very well and seperated.
The routing of the vacuum lines on the actuator might be different on the new ones when you get them. All you do is install the line from the tee section on the mower to the inlet in the center of the actuator and then remove the filter from the old one that is at the very end of the plumbing and install that on the inlet that is on the outer edge of that actuator. Good luck!