Alan:
I installed the de-celerator on my 96 at 96K miles. As of now it has 258K. I had one problem and that was fixed right away. I've seen some folks fuss but I've had good service.
You will not need to change the springs if setting your pressure at 30 lbs is right for you. As you may deduce, the stopping ability is less with the setting at 30 lbs. Mine is set at 30, and at times I like it that way. Sometimes I wish I had more but I like being able to maintain speed down a hill rather than have the brake on and off, during the decent. I may change to the 60 lb springs and set it at 40 lbs. I think that may work a little better for me. I'm towing 15K lbs.
As far as the brake goes, I like it very much. Under the truck and not hung on the back of the turbo. When I went to the 4" exhaust, with a little modification, I got it changed and it's still going. I like the O/D 2 speed too.
. . Preston. .