Boost spikes are quite normal, I wouldn't worry about it.

As for trying to up the boost without a corresponding increase in fuelling, I think you could easily end up damaging the engine.

From what you have described, it sounds like it is behaving normally, i.e. the boost diminishes as the revs increase. A good test is to hoof it up a long fast motorway hill, the boost should hold at 1 bar all the way up.

If you want t make it go quicker, get a remap done.