Hi, the 1 nF and the 3n3 caps (yellow) were mods that Nils Olof Carlin suggested and are meant for trying the best value fr C5. What they do are explained in the end of the manual "suggestions for modifications", "if C5 is increased the circuit will cut high frequencies quicker. If C5 is reduced it cuts high slower. .."

The other cap, 2u2 (black, round) is if you want to change the release time some (some words about it in the manual). You can put the 2u2 in the position "C12A(mod)" and then connect a wire between the holes S2-2 and S2-1. This will increase the release time a bit. If you want to change between the new release time and the one you had before, cut the wire and connect each end to an on-off toggle switch.  

Great, thank you for the advice moody.

Hi moody,

I was just checking and I could not seem to find an on/off toggle switch. I could only find on/on (SDPT) or on/off/on (DPDT). What kind of toggle switch are you referring to?

You can use an on-on switch as an on-off switch if you just use two pins of the on-on, the center one (normally) and one of the other. So if you have an on-on, install it in the box and connect one wire to the center pin and ground one of the other pins.