I switched my Turbo from the T25 Garrett to a 16g TDO5.  I have been having to get my car beyond 3500 RPM before boost actually begins. 

Is this a problem or is this normal before boost? 

Should it kick in a lot sooner or am I doing something wrong?

Is there something that I am doing incorrectly or do I need different sensors and other components to go along with the turbo swap?