Intel's Turbo relies on the OS being able to communicate hardware temperatures to the cpu, which it does with the thermal management component (subsystem) of ACPI (acpi_thermal driver).

However, its likely that ACPI is working fine and that the addition of the high-end XM chip to your system has probably increased the temperatures of various sensors in and around the CPU, since its a 55W TDP chip (not the usual 45W of the mainstream QM series chips). It won't turbo likely because ACPI reports that the hardware is already at the high end of its thermal envelope (turbo only overclocks the chip when there is "thermal headroom" to spare). Try running your G73 in a cold room (open the window in winter) or even a walk-in refridgerator and see if it turboes then: if it does then 55W TDP is simply too much for the G73's cooling system to expect it to overclock routinely at room temperature.