I have a2006 93 sportwagon 1.9 TiD 150. Nice car - not quite the build of my old 9000s - but capable just the same. Any perusal of the forums will reveal these cars to be tempramental beasts and mine is no exception. What is quite clear is that this is a car that needs to cover high-speed miles in order to keep the emission control system properly functioning. Even then they can throw tantrums - mine went into limp mode after six hours on the French motorway system. Luckily I carry a code reader and interrogated the OBD which threw up a "Turbocharger Overboost Condition" which when deleted sorted the problem. Six months later the car started losing power above 3000 rpm, went into limp-mode and threw up the code "Inlet Air Leak", again the OBD cleared the code and the car functioned correctly until a couple of days later when it again lost power, went into limp-mode and threw up "Turbocharger Overboost Condition". Clearly something wrong! A trawl of internet horror stories and I begin dreading what the problem could be.
Well to cut a long story short it's probably wisest to look for the simple and cheap things first - pull off the engine cover and check everything visually. This revealed a perished vacuum hose - a £2 fix and the car is revving but not as it should. Another look and I can see that the intercooler hose where it enters the inlet manifold appears to have moved slightly - yes the threads on the hose clip are knackered. £2.50 more and with the new hose-clip the car is fixed.
MORAL - before throwing your money at the problem, cast your MK1 eyeballs over the problem AND get an OBD Code Reader! I hope this helps someone who's scratching their head at another dreaded EML and thinking about remortgaging to fix their car!