No power? Downshifting on hills?
Where are you driving, in the middle of the Rockies or just a cruise up Pike's Peak? I have a 2002 Impala with the 3400 and it has plenty of power. It doesn't compare with the 396 or the two 427's that I once owned but it's good enough to drive on an interstate without problems.
I drive through the mountains of PA and VA frequently and use my cruise while doing it. It's rare that the transmission needs to downshift except on the worst hills. Methinks that your rental car may have been purposely detuned by the rental agency to rein in the wild drivers. Hurtz used to do that but I don't know if it's still being done by anyone.
My two-year-old Impals is a good car and the more I drive it, the better I like it. BTW, in three years, I've had no repairs made on the car and my only expenses have been routine oil and gas. The only problem I find is the "ultra-cheap" Uniroyal tires put on at the factory and once those are gone, I'll be a lot happier.
%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%% There are two classes of pedestrians in these days of reckless motor traffic - the quick and the dead. ~ Lord Dewar 1933 ~
Climbing into a hot car is like buckling on a pistol. It is the great equalizer. ~ Henry G. Felsen 1964 ~