Hi Mike, it actually happened for the first time on my way from Adelaide to Canberra before anything was touched. Maybe something broke during the long trip, I am not sure.
No coolant flush was done, however one of the line was leaking water/ coolant a little bit. The clamp was tighten up and a bit more coolant added.

Checked your map sensor? or are these AFM?
tried some injector cleaner, use the toyota stuff, very very good, but over do it, will kill the injectors, use it every 40,000kms had similar issue, cold starts would run rough, ran injector cleaner, fixed it, perhaps the CSI was a bit clogged? not 100% sure.
nothing as severe as your issue tho.
check the basics, plugs, leads, make sure its at correct timing, (put into base timing mode)
check coil for corrosion etc etc,
might not hurt to do a comp test, make sure you havent blown a HG as once warm it can reseal if minor.

i think the problem as others have said are in your adjustment screws tho, but wont hurt to check those things however.
depending on kms aswell, wouldnt hurt to stick a new 02 sensor in, worked wonders on mine, fuel economy was restored from 14l/100kms to about 8-11l/100kms
and power was returned. best 100$ i ever spent.

I get about 450-470mm Hg when cold and 500mm Hg when warm. Not a huge difference, but yeah, some difference.
The cold start injector switch is most likely the cause, and hopefully it's just that since it'd only be a minor annoyance. But I will need to have the rest checked out anyway.

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So the injectors were not 100% clean. I would suggest you change your fuel filter immediatly and run some nice fuel cleaner and premium fuel . This probably also explains why your having bad fuel economy
Cheers