Its what MJ said, a heavy flywheel, coupled together with an ECU design. If you shut the throttle too quickly on catalysed cars, you destabilize the flow and possibly the mixture of exhaust gases through the cat, decreasing its life.

Modern cars hold the ICV open slightly when you shut the throttle to prevent the engine revs dying back too quickly, and to keep engine mixtures more consistent, to try and preserve the cat.

Added to the fact the 1.7 that MJ is used to driving (in the loosest possible sense ) has the smallest flywheel in the world! Revs really are very fast changing compared to the other 2 engines.

Hmm, interesting, thanks Andy.

Looks like the 340 and 850 are at the two extremes.