08 Revving more than it used to uphill

Have you noticed a change in MPG?

If not, I'd say it has to do with something happening to the car that made you notice the noise more... Maybe you lost an underbody panel or some sound dampening material has come loose?

 

1. As always, check the 12V battery. If it has a shorted cell, it will draw continuous charging power that just goes into heat.

2. How's the HV battery? Sudden fluctuations from high to low in the SOC display? Is the battery cooling fan running audibly?

3. The engine may be putting out less, and is revving higher to compensate. Throttle body clean? How are the MPG's ?

This symptom is seen here often enough. Spending a little on an OBDII port/USB interface that allows to run a free program like Priidash on a laptop can help sort this sort of thing out.

 

Normally you'd expect the MPG to be a little better with the Ecopias.

Have you noticed any anomalies in the state of charge (SOC). It is fairly normal to hear the engine working harder to accelerate or climb hills when the SOC is low. If your SOC is suddenly much lower or more varied than before then obviously it could be a problem with the traction battery getting weaker.

If the SOC is behaving normally then it could be a problem with the HV battery cooling. Even if the SOC is good, it won't contribute electric power properly if the battery is too hot. Take it for a decent drive in warm weather and then while in ready (and with engine off so you can hear everything well) place your ear near the vent at the back seat and listen for the fan. If you've driven in warm weather you should hear it running fairly quietly. If you don't hear it at all then there might be a problem with the fan not turning. If you hear it really loudly then the battery is probably getting too hot (could be obstructed fan/vents, or it could be a failing battery).

Thirdly, I think that you might get similar symptoms if the inverter gets too hot, so definitely check the reservoir (near the inverter, in ready mode) and make sure you are getting good coolant flow.

 

+1 on checking for inverter coolant flow.

The ICE works with MG1/MG2 to drive the wheels. If the electric portion of the system is overheating somewhere, then the torque from MG1/MG2 is reduced as a protective measure, and the engine works harder to compensate. It appears that the improved pumps in the later GenII's are not much better than the previous failure prone version, and there are reports here of replacement pumps failing as well.

But your miles are low so pump failure would be surprising, though not impossible.