Chris,
I know my slammer has a good squeak and I know it catches fish but I don't know if the squeak is what makes it catch fish. It caught fish before it really had a squeak and continued to after it got the squeak. I'm sure it helps to have a noisy plug and at the very least it might just call in some fish to come have a look but I don't think it would be the one factor that would cause a 15lber to bite the plug rather than following it. Can't hurt to have a squeaky plug, like I said it might draw a little extra interest. What you can do is chip the paint off of the insides of the screw eyes in the joint so that they're metal on metal instead of paint on paint. After awhile the paint will rub away like on mine, but if you're in a hurry you can give that a shot.
-Brian