Unless you are experiencing direct gasket failure symptoms, there are many other options to consider when diagnosing cooling problems. It could be that your radiator is partially clogged. How old is the radiator? It could also be that your lower rad hose is missing the spring, and partially collapsing upon throttle. Also, that 160 degree thermostat in an otherwise stock system IMO is way too low. The ECU will be misinterpreting sensor input, and may actually cause the engine to run warmer. Another thing to check which I just had a problem with, ensure both your low speed & high speed fans are operational. To check low speed, turn on your A/C & watch for the fan, it should come on within 2 seconds @ any engine temp. Also, what is the general condition of the coolant in the car? At those temps, its possible a poor mixture could cause trouble. Perhaps try flushing the system & adding a mix with greater percentage of water, for better heat transfer. This will also help rid sediment & improve flow. You could also check your water pump, to ensure it is operating properly.
These should provide a start, let us know what you have done so far & what exactly is happening.