The following changes will improve the speaker and headphone audio. New C204 is soldered on TOP of IC5. This helps to correct faulty deemphasis in WFM mode. These changes modify the buffer amplifier that drives the TAPE OUT jack. If you don't use this jack, these changes may be omitted.
Helps bass response.
Q23 is surface-mounted. Helps bass response. Most of the changes noted above correct weak coupling between stages at low audio frequencies. Carefully performed, these modifications will unleash its potential audio performance.