Idle Problem

throttle body wedged open some how ???

You have developed a vacuum leak. check for blown off hoses/leaking couplers!

sounds like a vac leak.
I get this on mine though it jumps exactly the same amount.. I can cure it with the idle screw.. then a few weeks later it jumps the other way again.
Stick a timing light on the crank and check you are getting the same as what the megasquirt says.
That will rule out a timing issue i.e. borked cas or worn key way.

Clean your TB and ISCV, etc!

Top result, sounds like you managed to resist the temptation to play with your ems settings which in these circumstances is just too easy to do.

Glad you got it sorted.

ha nice 1

Phew! Well done matey.