I have tried a number of tweaks over the years but few have remained in my system. They might sound good one day and sound worse the next. The ones that have survived are based on sound Engineering concepts like resonance and vibration control.
Also, sometimes a tweak to address problem A introduces problem B. A good example of this is the use of ferrite cores on power cords. They do reduce the amount of RF coming in on the AC supply but, unfortunately, increase the AC source impedance as seen by the device. Power amps (and integrated amps) are susceptible and may become current-starved during dynamic conditions with a negative effect on sound quality.