What size inlet pipe for Cats?

[S6 Devil]

I'm looking at getting a pair of cats from cats2go for a 4.0l S spec engine. They have two different sized inlet pipes, 54mm and 57mm, does anyone know which size I need?

www.cats2go.co.uk/Default.aspx?PageID=15&CartI...

[Night Rider]

Hi, 54mm is for the std system and 57mm for the S. Best to measure the pipes after the cats as the headers are the same.
Rob

[S6 Devil]

Night Rider said:

Hi, 54mm is for the std system and 57mm for the S. Best to measure the pipes after the cats as the headers are the same.
Rob

Thanks Rob, will get them measured.