ticking-rattling noise when I accelerate

My 95 Chevy Corsica (2.2l, 4cyl) makes a fluttering or ticking-rattling noise when I accelerate.

The sound it makes though is hard to describe. Not a heavy rattle but a sort of light flickering sound when the engine is warm and I accelerate. It totally dissapears when coasting. It is like a faint burst of spark knocks.

Hard to pinpoint it under the hood since it can't be heard at idle.

On the net I've found the following possible sources:
1. lifter ticking (wouldn't this remain constant ?)
2. worn pistons/cylinders (at 100k miles the engine does not require oil top-ups)
3. loose piston wrist pins

any suggestions are welcome

tia
FuelSaver

It could be an exhaust manifold leak. Soemtimes manifolds seal well when cold, but have a slight warp or crack that only opens up (thermal expansion) when it gets hot from running.
Depending on the leak location it can be fixed by tightening the bolts, using a new gasket or, at worst, a new manifold. (Get one cheap from a wrecking yard. )

It could be pre-ignition, or 'ping', if your knock sensor has failed. Try a tank of premium gas. Sometimes an ignition timing problem (too much advance) can cause this, but I believe your car has a non adjustable ignition timing set up, unless the trigger wheel for the ignition has shifted (unlikely)