Prius limps on slight hills, does not respond to accelerator

We have an 05 Prius that has an odd problem. I noticed it last winter once or twice but now it's happening to my daughter all of the time. When getting onto a slight incline, the car will limp along and not respond to accelerator input. It's almost like it just idles along and then will eventually start working again. The car is throwing codes for the catalytic converter (it needs to be replaced) and the O2 sensor (related to #1). I don't think the cat is blocked, just old (I may be wrong). It's also throwing a MAF error and last year when this started, I replaced the MAF sensor (it happened coming home from an oil-change place and I thought perhaps they overfilled it). It seems to happen mostly when it's very cold out. I have no problem putting a new cat on it, but with 270k miles, I don't know if I'm throwing good money after bad. Any thoughts or suggestions?

 

Thanks for the response. I replaced the hybrid battery in August. I've read a lot about folks getting a MAF sensor error even by simply opening the air box, which my daughter did by mistake trying to find the fuse box one night last week. Oddly, the first time it happened after the oil change, the tech had also opened the air box to inspect the filter. After I replaced the sensor that didn't occur again until now. I know the CAT is shot and the O2 sensor has been shimmed a couple of times to compensate and prevent codes, but I'll just have to tackle that problem at this point. Just worried that this might be indicative of something else and that despite being in surprisingly good shape, I'd be wasting money. It amazes me how this car has otherwise held up.

 

One other thing I was worried about was a recent recall notice I saw about some type of water pump wiring short causing the car to stall. That's essentially what happens. You basically have to coast to the side of the road. If you pump the accelerator, nothing happens but then suddenly, it will return to normal.

 

Just an update on this. Took the car out this weekend for a test drive to see if my daughter's description was accurate. Seems that the gas engine was actually shutting down (I was able to force this condition by accelerating really hard - it coughed a couple of times then threw the red triangle of death). My daughter did not get the triangle but I think I was just pushing it harder. Ends up the "limping" was falling back to the electric motor alone, causing the low speed and lack of throttle response. I ended up calling a friend who used to be a Toyota mechanic. He suggested cleaning the MAF sensor again or replacing it with an OEM one. I did the latter and interestingly, the new one looks a lot different. The old has a cup-style sensor which seems to pull air down through the cup and out two small side vents. The new one is just an open circle through which air passes (as far as I can tell). The MAF code cleared after cycling the engine 3 or 4 times. Drove it about 60 miles since then and so far, the issue has not occurred. Fingers crossed! Still going to replace the CAT and O2 sensor so it'll pass inspection in May, but hopeful that this was the root cause of this issue.