Usually if there is a CPU bottleneck then it is CPU usage that will be near 100%, not GPU usage. However that's just a generalisation.
So, investigate the CPU issue. E.g., run some kind of CPU stress testing program (e.g., LinX) while running something CPU-Z and RealTemp so you can see what's happening. Check whether the CPU is reaching full clocks and then throttling down for some reason, OR if it's never reaching full clocks. In both cases, I suspect you will have grounds for starting a meaningful dialogue with Intel about the issue, and possibly an RMA of the CPU.