Just fitted a full replacement exhaust to my 740 2l estate. Dead easy
job, took an easy evening and most of that was getting the $*&£#
downpipe to unbolt from the manifold without breaking anything. Lucky
really - I went on holiday in it the day after!

One puzzler though. It's a Bosal system, supplied as 6 pieces and with
a number of U-bolt clamps all together. All the clamps are 58mm, except
one that's 54mm. As far as I can see, it's the same pipe diameter all
through, so what's with the one skinny clamp? In the end I went to the
shop up the road and put another 58mm on it.  Anyone got a magic book
of exhausts handy?

My own fault I needed it really. The complicated add-on hanger that
supports the centre box had rusted through and the dangling weight
caused the tail end of the downpipe to shear off whilst driving. If I'd
checked it more regularly I'd still have needed to replace most, but I
would have saved myself the broken downpipe that otherwise had little
wrong with it.