I've been doing some reading, and apparently the MK4 golf TDI mid pipe (exhaust), is a bolt on fit without modification, is the same diameter as the standard exhaust, and is straight through.

 

For anyone who has fitted one of these; does the part in this pic look like the correct one?

 

I've just checked the part number for an Octavia 1.9 TDI, and it's the same as the MK4 Golf as above

It is not a 'bolt on' you need to cut the pipe before the backbox as I don't think there is a break in the petrol pipe.

But yes, the parts are the same.

Edited 20 March, 201412 yr by michael1

And also the consensus is that you need to chop the flare off the front of the mid section, as the diesel downpipe is sleeved into the mid section, and the petrol uses a joiner. I'm going to be doing this myself shortly.

I'll order one up and get it fitted next weekend then