Sometimes I'm very hard to hear,
A sigh can be hard to hear.
So listen up and strain your ear.
Sigh sounds like sie, which apparently means "to strain" among other things.
With sixteen added, I'm twenty-three.
Sigh + P (16th letter) sounds like "psi" (23th Greek letter).
Or, with fourteen, I'll wave at you.
Sigh + N (14th letter) sounds like "sign".
Bring me low and I'm just storage,
Sigh + low sounds like "silo".
But call me up and I'll do removals.
Sigh + phone sounds like "siphon" (from Tom)
Ancient outrage sends me to space,
Sigh + fie sounds like "sci-fi" (from Gareth McCaughan)
But enthusiasm helps me to fit right
Sigh + zing sounds like "sizing".
Title: Oh, what's he posting riddles about now?
"Sigh... What now?"