What are 5 pin Link plugs for please? Do I need them in empty sockets?

Assuming you are talking about a 202, you will find all connection details in the manual. If powered by 200 you need all the plugs in place or it won’t work. If using a napsc you remove the paddle plug. If using a hicap you remove the little round one. 

My familiarity with link plugs are in the Nait XS, SN2, and CD5X; all "paddle plugs" I suppose. The units come shipped with link plugs in place and are required for them to operate. If you add a PSU the link plug is removed, disconnecting the internal power supply to the pre-amps (or for the CD5X, it's analog output power). The PSU is then connected via a SNAIC. There's no need for link plugs in empty sockets AFAIK, unless you are removing a PSU, in which case the plug is essential.

Many thanks for your two replies. I thought they MIGHT be interference-busting shorting plugs, similar to Russ Andrews' 'Shorties'.

I will ignore their existence then, as I clearly have no need for them with either my AV2/NAP150/NAP175 AV system, or with my other Naim units: a Superline & Hicap2, and an n-Dac & XP5 XS.

Thanks again, David

A simple rule is that if it works without them, you don’t need them. 

I think that would be a very appropriate motto for me to adopt! I often try too many gizmos! Cheers!