Losing power going up hills after installing new accelerator pedal sensor, then having it programmed. What's going on?

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I spent last spring working on my grandkids 2008 GP, and in trying to clear some codes, I installed a new gas pedal/sensor. The main problem ended up being it needed it's transmission rebuilt, and it took all summer to get that done. (Busy transmission shop). It's now running well and is back in the hands of my grandson, who texted me this evening and told me the car is running fine most of the time, but it's losing power going up hills. I scanned it and got 4 codes that all relate to the accelerator sensor. I paid a shop to come out and program the sensor after I had it in. Is it possible that something that was done while rebuilding the tranny might have erased the pedal sensor programming? He's in college and will be coming over tomorrow after classes so I can put the scanner on it again. He let me scan it today because an issue that it was having last spring was the 'reduced engine speed' (limp mode) message was showing up on the screen, although it didn't go into limp mode. I was hoping this was caused by the transmission problems, but it's still coming on, but not reducing the engine power. But it's losing power going uphill now. I meant to write down the codes but forgot to, so he's coming over after classes tomorrow and I'm going to take it to the shop that programmed it to see what they say. If anyone has had this problem, let me know what you found. Any and all comments, suggestions or ideas would be welcomed. Lee

 

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In case anyone is listening, I took the car to the shop and they tested the gas pedal sensor and it was giving eratic readings. (Bounced back and forth from having voltage to having no voltage. I ordered a new pedal from rock auto, took it back to the shop and the mechanic was getting the same eratic readings on the new one. He told me that a line off the pedal goes to the throttle body, and he checked the connector and the line and couldn't find anything that looked wrong. He said the connector was clean and he put some dielectric grease on it to see if that would help, but it hasn't
I'm wondering now if it may be the throttle body. Although I put a new throttle body in a few years back, my daughter sold the car to someome who never licensed or drove it, parked it on their property for a year and let nature take it's course. I did a partial cleaning of the tb last spring when I was doing some work on the car when we found out its transmission needed rebuilt. I didn't pull it off I just used some spray cleaner on the butterlly valve. I'm looking for a new tb now, and it seems like they've become harder to find. Either that or ridiculously expensive for a throttle body. If anyone has had the problem of losing power going up hills or taking off from stop signs, let me know what you found out about the problem. My grandson is a high school senior that attends college every day for his senior year, so finding open times to work on it is tough. But I need to get it fixed right. Thanks for any help or comments.