This turned out to be a slowish job as the some brilliant engineer decided to make the two open ends of the Y-piece join between the subframe and the steering rack where there is bugger all room to swing a spanner.
It looks like I had to undo the original clamps. The rear one was a piece of cake. The front pairing was problematic not just because of the restricted access. The last person who owned the car had changed the exhaust from this point rearward and (in)conveniently utilised the original clamping arrangement of M7 bolts and brass nuts. They weren't tight, but I did have to use a pair of 11mm spanners to stop things going round, and round, and round. Plus the area was a bit oily. When I say a bit, I mean quite a lot.
Helpful where the new clamps I received with the IMASAF Y-piece:
IMASAF 02.50.53 1 by
macplaxton, on Flickr
IMASAF 02.50.53 2 by
macplaxton, on Flickr
Although these use M8 nuts, I crucially didn't have to hold the bolt and I could orientate the passenger side one so I could get at both the nuts from underneath the car and with the driver's side one I put one bolt in one direction and the second bolt in the other direction. This allowed me to tighten one up easily from below and the other by climbing up and "planking" across the front of the engine and reaching down to the upper nut.
With the Y-piece successfully gooed in place. I looked at the middle and rear sections. The middle bit wasn't looking that great. The rear was looking better, but the join between the pair would probably be too much grief to separate. Luckily taking up space in my shed was a middle and rear section in stainless steel which I acquired a good few year back as part of a job lot of GS bits. So I decide to fit the lot while I was at it.
Stainless Steel Exhaust 1 by
macplaxton, on Flickr
Tailpipe is bent a little different:
Stainless Steel Exhaust 2 by
macplaxton, on Flickr
Collar and grub screw that holds the right-hand mount from sliding off the rod.:
Stainless Steel Exhaust 8 by
macplaxton, on Flickr
Having changed the Y-piece I looked at the old one and couldn't find the hole I thought I remembered seeing.... I started the car up after I'd finished fitting everything and the blowing noise was still apparent. I shoved my head under the bonnet and found my problem really quickly:
Hotspot pipe rear offside 2 by
macplaxton, on Flickr
DOH!
I think it was that all along and the rest of it could of stayed on a bit longer. I'm really annoyed as I've been fixing things way long enough to know better. I think maybe a bit more sleep might help.