Some of the vintage pedals require an overhaul of all the old electrolytic capacitors. It can make a HUGE difference in the sound!
But how to keep track of which caps have been replaced and which ones haven't? My trick is to leave the legs on the caps until the project is finished. When the whole project is finished that's when it's time to clip off the leads. In the meantime, leave the leads until the pedal is sounding great.
Here's a vintage Ibanez Flanger with a complete capacitor replacement job.