So get an overhaul for around $200. If that doesn't do it - sell the anchor and get something you like.
Both are cheaper than a psychiatrist.
Do let us know what the shop says, please. You've piqued my curiosity. The old 1980's Shogun road-bikes were notorious for having some peculiarity built-in that just made them slow. No one ever satisfactorily explained why. The components were good. The wheels were okay. They were really slow! Bizarre.