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