Well I think whatever the updates do, somewhere along the line things change some for the better and some for the worse.
Very true, I have put later cals on Transit TDCI before and it's made them more noisy for example.
Trouble is, once you have put the latest cal on, it's very difficult to change to an earlier one. Easy to sit here and say it but there is one way that I know of, which involves blanking the PCM and going into a routine with 'no-comms' then adding an earlier cal number (If known) That is of course if this is still supported on recent versions of IDS software. Ford do take off useful stuff like that sometimes when they revise the diagnostic tool software!
EDIT - Looks like the original PCM part number for mk2 RS is 9M51-12A650-CG according to an ECU for sale on Pumabuild.
http://pumabuild.com/pumacat/product...oducts_id=2250
Previous poster stated update is CL So in theory it should be possible to blank the PCM and then add the original CG part number to get it back to an earlier cal.
Surely the dealer should know this or if not be guided by Ford technical to do so?