I've experimented with bridge pins before, but they never seemed to have much effect on sound. I find r
eplacing plastic bridge saddles and nuts (the parts that transfer vibrations from the strings to the wood) with bone makes a difference on less expensive guitars. Another tweak that's worked for me in the past is install a metal bridge plate over the damaged wooden bridge plate inside the guitar. It improved the sound on that guitar and seemed to help it stay in tune.