Carb spacer

Maybe a silly question but what's the advantage of increasing the height of the carb on the intake?

Currently I have 1" spacer on a hi rise m1 single plane intake,

Reason I ask is im trying to overcome a top end issue, it seems I'm either loosing power at the top end somewhere ( i do know I have a under fuelling issue I'm in the process of dealing with)
And I wonder once this has been disguising the fact I could do with a higher rise?

Help please

The straighter the line from the carb butterfly to the intake valve the better the port flow(Yes there is a LOT more to this, just trying to make it simple) so a spacer helps this out a little. It also give more volume in the manifold so cyl can share volume more equally at top rpm.

Get your fuel system figured out, and the space will be but minor Candy after words:D