Thanks for taking the time to get back to me. I have spent a lot more time on my model and I am starting to get results. I have taken everything that ye have said into account but I am still unsure if I have correctly implemented a bi-directional digital waveguide. I think I may be close though.
I am taking this model from a paper by Matti Karjalainen and Vesa Valimaki. The title of the paper is "Plucked-String Models: From the Karplus-Strong Algorithm to Digital Waveguides and Beyond". I am trying to implement the plucked string with bridge output model.
If any of you could shed some more light on the subject it would be much appreciated. The two updated files are attached.