Car feels....lazy

Car: 2008 Charger R/T w/ 78,000 miles.

I recently did spark plugs, oil, oil filter, air filter and ran some fuel injector cleaner through a 3/4 full tank of gas. I also disconnected the battery to reset the cars PCM/TCM parameters and cleaned out my TB's butterfly flap.

While the above has net me a solid bump in MPG from when I purchased it, the car feels....bland. The MDS kicks in a lot more than I'd like it to, but that's a story for another time.

In any case, the gas pedal doesn't feel soft like in my old 06 and 07 R/Ts. It feels a bit heavy to be honest, and not as lively. On my older cars, the slightest tap of the gas would have them going sideways. On this car, it takes a lot of effort to get the gas pedal moving.

Also, on the highway, it feels lazy in terms of picking up speed. If I'm doing 65 and want to speed up a bit to pass someone, I have to REALLY give it a push on the gas pedal to get her to speed up adequately enough. Again, the pedal feels rather hard to push down and requires a heavy amount of input to get a good response from the throttle.

I'm pretty much all out of ideas. The MPG is there, but I can't seem to figure out why the car still feels so lazy and sluggish. Any thoughts or ideas? Things I may be overlooking?

I tried to do the throttle reset, but having come across a few different processes, I am not sure if any of them work. Buddy of mine suggested maybe changing the differential fluid or the fuel filter, but I don't want to just throw parts at it blindly....