I was wondering which focus st it was that the tdci shares its intercooler with? The 2.0 New one or the old 2.5???

Its the old 2.5 - but its not an upgrade, my information is it will restrict the Mondeo, as the stock mk3 (Mondeo diesel) intercooler has 2-14" inlet and outlet , all the MK3 diesels have the same intercooler, from the 90PS di to the ST-TDCI - the ST-TDCI has 155PS and can produce 180+Hp and 400+ Nm with the stock intercooler

Best to discuss your present and future modifications, how much you wish to spend, etc etc, like changing the intercooler is a waste of time - a remap or tuning box will make the biggest difference, followed by a back-box delete, decat, EGR blanking, resonator blanking, in that order (biggest to smallest improvement)

Once you have done all that, an intercooler upgrade may be worthwhile (but not a stock Focus ST one)

It gets a bit complicated/ technical when you statt talking about pressure drop, internal volume, thermal inertia etc

edit - here is another post with more details - http://www.fordownersclub.com/forums/topic/43988-upgraded-intercooler-advice-needed/

That's good info mate. Thanks a lot. I appreciate that.