nulu, alabbasi,

ty for the suggestions.

accumulator would be simple answer but i mentioned that the engine was running rough, and my mechanic quick-sprayed degreaser along each bank of injectors. when he did that, the idle was smooth.

based on the symptoms and the temporary cure, he concluded that it was injector seals, slowly breaking the vacuum when engine is off. Could be one, or the other, or both/all.

thoughts?