Right a bit of an update to this frigging saga!

The bung seemingly has no effect whatsoever - I'm too dense to tell if there is a drop in torque (doesn't seem to be, but could only be proved on the rollers I guess). It doesn't even really sound any different, so may well put the resonator back in at some point (although having it removed makes for easier removal of the manifold (more room to grab hold with and doesn't foul the stepper motor)

Furthermore, I took the car to a mate who is a mechanic for some race team, and while it was running he did some trick whereby he sprayed Air filter or Carburettor cleaner (?) around the manifold gasket so see if any would get sucked in and sure enough the engine coughed and stuttered a little.

Looking at it run, i think you'd be hard pressed to notice - but it seems to suggest there is a slight leak no?

So may well sandwich the PTFE gasket with paper gaskets at weekend to get a proper seal once and for all.
I'll be a dab hand at removing the thing by then (will get a proper torque wrench this time too)

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Team: Moonstone GTI-6™
Team: Working air-con™