It's something I looked into doing with my Leon. It doesn't appear to be that popular a mod but if done right I think it can look good. Your not going to get a massive change in the car's performance but little things here and there will be better. I haven't done it yet so can't give you any personal experience.

This is the guide for the Leon Cupra, I know it's not the same but it might help a little bit?

http://www.seatcupra.net/index.php?option=com_content&task=view&id=511&Itemid=6
 
im just trying to rule out as much electric noise as poss

I'm looking into it for the same reason, my head unit is so bad now that I cannot use any external device that also needs a 12 volt feed. If you look at the Leon guide you can see the items that are earthed, which from memory are;

Bodywork
Battery
Throttle body
Engine block
Alternator (I think?)

I wouldn't buy a kit though, the materials can be bought much cheaper if you are happy with crimping or soldering the terminals.
 
Get pic of mine some 2morow if the weather good,
think mines r connceted to: alternator, coil pack, ecu earth (under windscreen panel...
 
Yes engine bay needs a clean..lol

Image0373.jpg


Image0372.jpg
 
Inlet manifold makes sense, I would guess that the gasket is designed to be airtight rather than electrically conductive. The alternator is mounted on a couple of adjustable bolts, again not that great for electricity.

I can imagine the coil packs being a biggy, unfortunately in my particular car I don't remember there being a common ground for the coil packs.

I can't see one for the chassis itself? I'd have expected one somewhere going to the bodywork?
 
Inlet manifold makes sense, I would guess that the gasket is designed to be airtight rather than electrically conductive. The alternator is mounted on a couple of adjustable bolts, again not that great for electricity.

I can imagine the coil packs being a biggy, unfortunately in my particular car I don't remember there being a common ground for the coil packs.

I can't see one for the chassis itself? I'd have expected one somewhere going to the bodywork?

yeh mines are mainly on the engine instead, as thats what consume smost current, There been differnt on cold 1 click starts and thats with worn stem seals...There is a connection under scattle panel where ecu earth and chassis is bolted... Works for me but can move it around if others like but dont want a spider web in the car with too many wires, :D