Yes it does alter fuel flow. Apparently, it also depends on the speed.
Here is what I got for the Su-27 in LO:
H = 600 m
IAS,km/h TAS,km/h N1,% FF,kg/min
-------------------------------------------
300 314 66(Idle) 18
500 523 80 35
600 627 82 41
-------------------------------------------
H = 9000 m
IAS,km/h TAS,km/h N1,% FF,kg/min
-------------------------------------------
300 500 66(Idle) 8
500 820 87 29
600 987 91 45
-------------------------------------------