How to disconnect wires from connector blocks?

[Radek]

I've been trying to relay the headlights on a 88 90Q, using relays from my parts car, together with their respective connector blocks.  The idea is to place the relays inside, on the existing panel, away from the engine compartment, moisture, etc.

However, I want to change some of the wires in the connector blocks for thicker ones.  To do this, I've been trying to pull wires out - I used small nails, pins etc. to unlatch the wires - without any success.  I'm talking about  connector blocks that have four (in this case) wires in them, all female fittings, that fit into a standard Audi relay with spade connectors. I don't want to destroy the plastic block, just to replace some of the wires that fit into it.  Is there a trick to it, or a special tool? 
Thanks.

Radek.
88 90Q
91 V8Q 5-sp.