So in my EL, when I'm driving along (most noticeable in dusk/dawn), and I don't have my parkers/headlights on, every time I apply the brakes the cluster/climate control/trip computer lights dim, when I let go off the brake they go back to normal. If I use parkers/headlights they dim like they should as normal.

So why do they dim when I brake?

probably just a bad earth. Add an earth from neg alt or neg batt to body or block and see how you go

You have the wrong brake globes or a faulty filament in one.

You require 'twin' filament 5/21w tail light globes, Not a general indicator ones.

You might be right about that one, had to replace one of my brake globes recently and it didn't seem to fit in properly. Like it works but it won't lock into place or anything. :S

Brake light loom bulb holder plastic bits that hold things in place tend to crack and disintegrate, bulb cant contact properly, earthing problems, yadda yadda yadda. $5 from a wreckers for a new loom and you'll be right