The maximum multiplier for an 8250U is 34 and your screenshot and log file show that the CPU is using the 34.00 multiplier so it is running at its full rated speed.
In the TPL window I would clear the Sync MMIO box and I would check the MMIO Lock box instead.
Try running a TS Bench 960M test. If this test reports any errors, I would increase the cache voltage. Some 8250U are only 100% stable when then cache is at -70 mV.
When you run a log file the computer has to be loaded actually doing something. Testing the CPU to see how fast it runs when idle does not accomplish anything. Run a log file while running Cinebench. That would be a more meaningful test.