So, knowledgable collective, what are your thoughts on this?

My exhaust primaries are very close in a couple of cases (1&4 and 2&3)

Most of the time they are quiet, but at certain revs they rattle together.

What can I use to 'pad' them apart about a millimetre? Is there any high temp thin rubber that will do the job?

Exhaust wrap?

Or pull them together with a stainless steel tie wrap (used to hold the wrap on?)

Hadn't thought of heat wrap, my head was stuck on keeping them apart...

Trouble is it is on the vertical section after leaving the bonnet, so I want to keep the appearance clean

Get someone to do a neat stainless steel tag/dot weld to tie each pair together ( 4 small tag welds, one for each pair) close to the bend(s) and they will hardly be noticed, but they will stop sympathetic vibration.

edit bit

just inside the bonnet should do it.

[Edited on 20/5/11 by jollygreengiant]

Good idea about the welds but under bonnet clearances are to large, the pipes only come together in the vertical drop to the bends before the collector.

If the clearances under the bonnet are too large, do you have space to weld a small SS bar in rather than just a little weld?