Yes, the throttle input values were the same and conditions also the same (airport, weather, time, weights) but with throttles assigned in FSUIPC I could not get the same airspeed as if I assigned it directly through the in-game controls.
There is also the issue that the automated flight engineer cannot maintain the airspeed indicated in the POH but as soon as I disconnect FSUIPC it would finally speed up to the expected speed.
It seems that your solution to rename FSUIPC7.ini and then try again resolved the issue and I am now able to get the same airspeed that I was normally supposed to get so that issue has been resolved at this point, after the creation of the new ini file. Thank you very much for your help in regards to this issue. I'm not sure exactly what was causing the slowdown on the old FSUIPC.ini but if you would like me to attach that I can do so.
Once again, thanks!