Engine Surge on Autothrottle

[Gringo6]

On one of my airplanes, at intermediate air  speeds (250 KIAS) the engine rpm will surge up and down when the autothrottle is used. The air speed doesn'i vary much however and holds pretty well.

There is a very small change that can be made in the .aiir file that will correct this, but I've forgotten what it is.

Can someone please remind me what it is?

Thanks,

[Strategic Retreat]

Would be useful for me to know it too... I have a MD80 that suffers from these below 200Kias and even retarding the speed AT responds to changing of speed in the Aircraft.CFG didn't work at all.