4.0 Shuddering and hesitating under load, feeling weak

I have a 2012 TRD Sport 6spd 4x4, 40,000 miles. For the last several thousand miles the truck hasn't felt the same as it did new. Under moderate acceleration or under load (pulling about 1,000 lbs) the truck will "shudder" under load and hesitate while it's trying to accelerate. I've also noticed it doesn't feel as gutsy down low as it used to. When I mash the pedal it doesn't react like it used to. This is the best I can describe it unfortunately. The truck has also developed an awful "rev hang" when shifting from second to third gear. As is the case with all of the manuals, it has a rev hang, however, it's substantially worse when shifting from second to third; something the truck did not used to do.

When I would mash the gas before it would accelerate smoothly and consistently, even if in a gear a little higher than it should have been, now when I mash the gas it will start to go for a split second, hesitate (and sort of shudder) and then slowly gain rpm's/speed but it sounds like the engine is really working hard.

Within the last five hundred miles I've changed the plugs, air filter, oil/filter and had the TSB done to address the spark knock. The truck was pinging very badly in addition to the problem described above so I changed the plugs and had the TSB done which addressed the pinging, however, not the other symptoms. Air filter hasn't helped either. I'm guessing it could be the MAF, fuel pump, or fuel filter? At 40k miles I don't feel like any of that should be a problem though.

Any help diagnosing what's going on would be much appreciated!

 

Did you scan for any stored codes?

 

Not yet, it hasn't thrown any lights.

 

Sometimes there will be a code stored even if the light isnt on. I would start there.

Fuel filter is considered self cleaning in the tank and suppose to last the life of the truck. Unfortunately there is a lot of things that will cause that issue. Bad coil packs, incorrect gap, throttle position sensor, fuel pump, maf, the plethora of sensors all over the motor and exhuast.

 

I'll take it to my local auto parts store when I get a chance and have them check for a code. Thanks!

 

The dealership said there were no codes stored, however, after having the TSB done the truck is still pinging which my dealership is telling me is "normal." I'm not really sure how to go about it from here as the pinging is obviously not "normal." I find it not only disappointing but insulting that Toyota is refusing to fix an issue whilst also calling me a dumb ass.

On a side note I did test drive a 2015 with an auto and I was actually disappointed. It felt a lot more "slushy" than my manual. I think I'll just wait out the rev hang until someone comes out with an aftermarket turner.