2008 1.2 polo bad running BZG engine

[richardhyatt]

good morning,
new member to this so hope I am complying with everything.
2008 1.2 polo petrol 3 cylinder engine code BZG

we have cleaned the throttle body and checked all the gears inside and can see the butterfly moving when plugged in(whether correctly is another matter) - we can see it twitching when ignition is turned on -
cleaned all the other pipes etc - no EGR obvious to clean

problem - it will not idle happily

when we run the car without the throttle body plugged in, it will idle very happily ironically , but when you re-plug the TB , and delete the code stored, the idle is no good at all and no power.
we shorted the battery leads together and cleared the ecu and we have yet to let it idle to operating temperature to relearn that bit

compressions are acceptable given that we cannot floor the pedal and check if the TB butterfly is ACTUALLY opening fully - but they are ok (and of course it runs nicely at idle with no TB plugged in)
all plugs new and all 3 spark well when laid on the head - all 3 injectors squirt well and cleanly when laid on the head

I don't want to throw money randomly at it , but any more suggestions please? - running out of ideas (maybe throttle pedal tps next??)
thank you for any suggestions

Update, run engine to temp whilst TB unplugged, idled well(better than when tb plugged in certainly)
Plugged TB back in , deleted any faults , run again but bad idle again.

Any thoughts please?

[Johntheo1]

It might help to remove the air cleaner and squirt a bit of WD40 or the like (carbon cleaner ideally) onto the throttle plate and leave for a few hours or overnight.
Also possible that you have a air leak, check any "hard" plastic pipes around the brake servo, these have a tendency to crack.