After 23 years any collagen should have degradated. You were most likely injected with something else, or your body formed granulomas around the injection sites. See a knowledgeable dermatologist or plastic surgeon in your area to discuss options. One treatment to consider...
From what I can tell in your pictures, it doesn't seem to me that there is a major scar on your lip. Did you have any trauma to the area during or after the injection? At this point, I think whatever may be causing the irregularity you are noticing (and I don't see any in the photo), you'd be...
Goretex implants were once used commonly for lip augmentation and are rarely used currently as they have been replaced by Juvederm or Restylane lip injections. Goretex can usually be removed from the lips using small incisions.