My '12 assault had a weird inconsistant bog at one point... hard to recreate it, especially when you were trying to show someone the issue. Turned out it was a broken injector wire that couldn't be seen inside of some casing... only found it by running the motor and shaking around wires while giving it some gas... the dealer ordered me a new harness under warranty. No issues since.
It sounds like spark plugs to me. Wasn't sure if it was doing it before new plugs or after you already put them in. Pros and turboes are hard on plugs. Might be something bigger but I have had them act similar and it was plugs.
Change the tps, set it and forget it. Those tps are a PIA, they seem alright when checked then you drive it and the go outa range. I am on my 3rd one now and they updated them, the most recent one is a little different. I was chasing this type of gremlin, and when I changed it she was good to go. Especially if it wont go into reverse, it stinks of tps outa spec. my two cents.