P0401 :(, pretty vague code Options

[b22ri22an]

says insufficent egr flow when i checked the code... car runs the same as before the light came on and from what i have read there seems to be many different things that could actually cause this code to come up, any insight? egr passage ways are clear and the egr is fuctioning.
replaced the ecu about 4k miles ago, a shorted fuel injector killed the last ecu and after replacing the injectors it still was throwing a number 3 misfire and wasnt juicing the injector, replacing the ecu fixed that problem and while the mechanic had the car to replace the injectors he had my throttle intake and egr sonic cleaned since he had the intake off anyway. btw the sonic cleaning made a huge difference in terms of throttle response you could litteraly eat soup out of my intake it was so clean

is it possible i just have a sensor thats bad? anyone have this code pop up, and more importantly am i risking damaging my engine from excessive combustion temprature continuing to run it with the light on, i mean i litteraly feel no difference from before it turned on till now