+1 per what
@scotman said.
Best to keep the older throttle body - even if there is a core charge.
Many times - the "poor idle" can also mean broken vacuum hoses or a poor seal that is leaking, causing surges in the idle speed and if too much air, it might try to idle up but will not hold that speed knowing it's got an air leak.
It should also have a gasket or if not one supplied, you should put a new one in when you install the new throttle body.
So even electrical connections to the throttle body, if this problem has returned like you said it has, might also mean the electrical connector to it, is faulty, as to connections and to the wiring failure - like a broken wire or a poor ground.
This may also mean the MAF sensor (if it has one) on the snorkel might need cleaning or replacement - it's connector needs to be checked too.
There are two variants of the engine in that thing plus the fuel it can run, Diesel and Petrol - and Zetec motor or a Mondeo variant Endura - so there's a wide variety of things than we can talk about, but to help you - what kind of fuel and motor does the MK5 have in it - a simple photo goes a long way here...