Am i7-2600 won't bottleneck a GTX970, generally speaking.
If games are optimized to use multiple cores, the i7 will still run amazingly. For games that are not multi-core optimized, you may see slight impacts in FPS vs latest gen i5's (even i3's) due to their stronger single-core performance.
Where are you seeing these 250+ FPS? Youtube by chance? You have to take what you see with a pinch of salt. You don't know the full setup, specifics on cards (at least, not always) and various other elements.
Ensure you're on the latest GPU driver, and have uninstalled older versions. Monitor your CPU usage and GPU usage (HWMonitor is a good tool for this, but there's numerous others). See if one is hitting 100% with the other falling...