A remap allows the bike to make use of more air in and more air out so no doubt the standard software will allow you to make small gains but a remap will have a slightly greater effect, an additional plus 10% if it's done very very well. It will help the bike feel better too by allowing it to run a touch richer and will protect the engine (but risk your ecu)
Note That most major gains in BHP comes from a higher engine RPM and that is much more difficult to achieve.
Don't expect more then a 15% increase in BHP without extreme engine modifications.
