Hmmm yeah not sure, when car is on the IAC sensor receives 13.8v on the middle wire which is normal I think. It only faults when I decelerate for a long period (I.e down a hill) then it goes into low power when I accelerate more than half throttle the first time after the deceleration, then the check light turns off and it drives fire until the next deceleration 

Time to pull out the multi meter and measure resistances. But doesn’t the IAC share some wiring with the o2 sensor maybe the old sensor blew a fuse or one of the ignition relays.

came across these "Paid" files   Spotlight Cover's : Headlight intake's etc not cheap BUT I thought some were neat   https://cults3d.com/en/design-collections/GiaoPX/subaru-impreza-gc8

codes cleared took it for a drive and code 24 popped up again after about 10minutes, wouldn’t let me boost fully and went all slowy  Idle Air Control looks like I’ll be pulling it out this weekend   

I didn't do it today, but quite a few months ago lol.  I finally figured out my shutdown issue on my Type RA.  The issue was it would start fine, run perfectly during normal even spirited driving.  When I'd go on track at say manfield, and start giving it some absolute spanking, about half track point the car would completely shutdown. I'd have to key off, and then key back on and away we'd go again.  It was repeatable and I couldn't figure it out for the life of me while at the track.    So, replaced the battery because A. it was old AF and dying easily.  Thought it resolved issue up until a couple months later I was at a gymkhana event here in hastings and it died under, again, heavy load, but this time the battery light was now coming on.  Sure as heck, I checked the voltage output on the alternator and I am getting bubkiss.  Quickly dip home, pull out a crappy old looking spare alternator I had, remove the old alternator, and the terminal for the positive is absolutely COOKED, with the nut literally welded itself to the alternator...  Slap this new alternator on, and rush back to do the last runs and fixed. Now to just do a cambelt/idler change as these are due.