It varies widely by tuner, you and how well your car response to it.
Example. While I only picked up 1 rwhp on the peak. I picked up 9rwhp under the peak and 10ftlbs of torque across the board. Throttle reponse is tons better, but I had my tuner put a very conserative tune on my car. My reasons were that in my area we get the oxygenated fuel, I've noticed less performance and less mpg with it compared to fuel I get elsewhere.
I've heard and know people that have picked up 30rwhp with a tune on a very lightly modded car, so you never know.