When its not in gear does it rev normally ie past 1000 rpm and beyond ? Try this plenty of times,are the revs smooth? on decelerations does it hang momentry at all?
What is the rpm at standstill don't rely on the taco do it on live data .
When you put it in gear check fuelling on diagnostics
Check current fuelling when in n and when in gear.
Also a dedicated diagnostics can do two checks on the throttle pot I think one is % and one is voltage check via pedle ie you might be getting a feed to throttle but the throttle itself should rise in volts .
Personaly I think its your fip its stuck under load
I had the same problem it would rev but in gear it would not get going until the revs passed 0ver 1000 rpm once back to tickover struggles to rev in gear without picking up revs first .
Like suggested unless your garage has a dedicated diagnostics machine it will only give you the basics .
Ps your engine management will only pick up a failed cps or needle lift sensor and maybe the elab Solinoid shut off same as diagnostics might only tell you somthing is wrong by reading live data for instance if my rpm was too low and the car kept stalling I would not get a code saying rpm too little but I might get cps failed or fuel quantity too low you need to be a bit of a detective with some faults not everything is black and white and served on a plate
The throttle pots connections
Also say with a nanocom , through the auto box ecu you can check throttle position,plus engine power , I'm not sure where engine power Derives from? and tally it with the readings on the nano under edc ecu throttle pot %( position ) and volts.im not sure about other diagnotics makers tho.