A couple of arbitrary contributors to the rev hang or soggy throttle response on a Duratec that I've noticed and propably worth mentioning. Fortunately, these are both easily fixed.
The first can be attributed to the plastic throttle body. If the car left the factory with the round rubber air intake hose jubilee clip over tight, it can distort the plastic body, compromising the throttle butterfly sealing. Whenever you take your foot of the throttle and close the butterfly, air can still creap into the engine past the butterfly plate, slowing down rev drop as the idle control valve grapples with the extra air load. And it gives an unresponsive soggy feel when you rev the engine.
The other is the throttle butterfly sealing. That is done manually on every TB using a tiny paint brush and applying a hard sealant. I have a couple of spares and they all have slightly different amounts of sealant. It results in the same effect as above if not perfectly sealed at source.
I did replace my plastic TB with a metal equivalent and spent some time sealing that. I thought something worthwhile if keeping the car long term so it all works very nicely now.
