It's all downhill from here...

[JoshsE34-M50]

My '91 m-50 has a slight hesitation under this condition: going downhill, coasting under no load (especially very steep hills), then hitting the gas.
Driving on a flat surface at, say, 55mph, then letting off the gas and reaaplying a few seconds later won't cause it; only downhills. I can reproduce the condition over and over-very consistent. It's not very annoying, except when I forget about it and it happens.Otherwise, it runs What should I think about- vacuum leaks, stomp test, piston rings, something with the fuel pump? 155k, uses an acceptible amount of oil, reasonable condition of tune.
I know the highest (or rather, lowest) amount of vacuum occurs when your car's decellerating. Any ideas?

[BillionPa]

auto trans?