+4 KW is fine. Minus or plus that amount is within tolerance specs. On the R32 engine, the tolerance is +/- 8KW!
You normally see +/- 3KW after a chain job, so I wouldn't be concerned by +4. To achieve the ideal 0KW, you would need to replace the intake cam sprocket as well, which obviously no one does. The VVT variator compensates for slight timing angle discrepancies, so I wouldn't worry about it. 1KW drift would make a difference on a diesel engine, but on a gas engine, it's fine.