Here's an interesting one for you. 

PD 130 engine (ASZ). I can hear a hiss from the driver's side of the car at low revs.

If I start to rev a little the hissing stops.

 

Thoughts?

Edited 20 September, 20178 yr by bspman

I suspect it's from the fuel system and probably nothing to worry about.

 

Does it accelerate as it should once on the move?

Mostly, ok. 

The car was remapped and that's when I started to notice it.

 

From low revs it can feel like the boost suddenly comes in (though not a massive amount) or, just after a gear change, it takes a moment to begin to pull normally.