i'm runnin raybrig hyperwhite all around... my fuse has been blown out a lot lately =( currently i'm runnin 20A in the fuse box in the car and 20A in the fuse box under the hood (supposely 7.5A in the car and 15A under the hood.)

is it bad running higher voltage fuse than stock? if it does wat kinda damage or problem it'll create?

 

The fuse rating for any given circuit has been designed to protect other components in the event of a large current draw such as a shorted wire etc. If you exceed the rating, you run the risk of burning wires, or worse, starting a fire.
That said, the rating has usually been set with some safety margin.
You can probably get away with increasing the rating some but 2 times is definately too much.