It's called getting used to the power.

Thats why we keep modding

That being said, there is a range of things you can do to ensure that your car is still running A-OK and its merely your "butt dyno" that has failed.

1. Check for vacuum leaks and loose connections
2. Ensure boost is the same
3. Ensure that your exhaust and intake aren't blocked
4. AFR check and compression test if you're really really worried.