RX4 power loss

Hi, wonder if anyone can help. I have a Scenic RX4, 2.0Ltr petrol. The engine is good with nice clean exhaust and no oil loss. On the flat it pulls well and appears to have bags of power until it comes to a hill or slight incline where it loses power. I am having to drop down gears to keep going, at one point I was in 1st gear, although it was a rather steep hill, but I don't think that this is normal. Has anyone else had the same problem and, if so, what did you do to correct the fault.

Thanks in advance for any help. :crazy: