A remap will never give a n/a engine a power boost like a petrol turbo or diesel turbo would get. But if you have done a few engine modifications then it all helps, especially if you have cams and exhaust manifold along with some of the usual modifications.
I did mine and I saw a difference pulled much better but figures of a remap for the z22se will be around 6-12bhp, torque about 6lb/ft.
I am a dealer for Celtic Tuning and it states on a standard engine:
Standard Power : 144bhp
Standard Torque : 149lb/ft
Modified Power: 156bhp
Modified Torque: 161lb/ft
Watch the first two minutes of the below video of me at Snetterton, before I start letting cars go round me. My friend in the car in front of me (Fiat Coupe 2.0L 20v Turbo, dyno'd at 234bhp) does not really pull away from me that much.
https://www.youtube.com/watch?v=Z0VNC8WJ1Ic