Hi
Just had a problem with mine with idle speed anything between 900 and 2500 and loads of popping on exhaust on overrun.
Checked all the usual suspects but everything ok, OBD showing no faults.
Turned out to be a split or battery acid corrosion in the inlet manifold where the vacuum pipe pushes onto it next to battery)
Quick blob of black silicon and alls well again.
Though id post this in case anybody else gets the same symptoms

Was this a 1.1 mpi?

It is an mpi
God knows how its holed at that point but although not much bigger than a pinhole it played havoc with the engines running
It had to be an air leak thinking about it now because when i blocked off the throttle body with the palm of my hand it still idled. Amazing how little air the engine will idle on