[sidemouse]

See, let me tell you the very first thing that created "lag" was the throttle "cable."
Did you know in the early days a steel rod linked the gas pedal to the carburetor's butterfly valve, when a driver stepped on it the message to the engine was truly as instant as one can get.
When that valve opened up the engine sucked AIR and that air rushed past jets in effect sucking FUEL in with it!

Then came cables, and these are not as responsive as rods because rods are stiff.

Nowadays we have sensors on the gas pedal that detect when the foot steps on it, send a message to the ECU, the ECU in turn sends a command to the motor inside the throttle body that opens the butterfly valve AND to the fuel injectors to start delivering fuel to the cylinders. One would think electronics are the fastest in delivering the message but have you ever watched this in real life? That butterfly valve opens quickly, but even at top speed the gears can't turn the valve as fast as my foot can mash the pedal to the floorboard. In fact, even at top speed that valve opens some kind of gradually.
The steel rod could deliver the message, if I mashed the pedal to the floor in an instant that rod opened the valve just as quickly.
Carbureted engines always were quicker right off the start, even to this day.
But the older cars also suffered from this throttle lag for different reasons, most of it to do with slack and looseness.

If a U-joint has even a thousandths of an inch of play in it that will create a split second of lag and that is only one piece that must function to deliver power along the way from the gas pedal to the wheels. U-joint, CV joints, all the same thing for the sake of this argument.

It's funny...
Like if you're planning on racing someone else, you actually have to PLAN on hitting that gas pedal ahead of the actual event of accelerating because if you hesitate you will lose.
Throttle lag, the bigger the engine, the more lag the driver will experience and thus the farther ahead of actual acceleration the driver must plan on hitting the gas.

 

[12 lt]

I will say this...
All high powered engines suffer to a degree from this "lag," even Corvettes.
We are so used to instant gratification, however in the real world it takes actual time to build things up...
When a driver first steps on the gas pedal it sets in motion a series of events, the reason we don't notice much lag in lower end vehicles is it doesn't take that long to go from a few horses to 80 or 100... But in a more powerful car it takes longer because it has to get up to more horsepower, there exists a distinct pause from when we step on the gas pedal until the engine has finally achieved the horsepower the driver had intended to gain because it just takes time to revv up to that...

No, it is not possible for an engine to go from 800 rpm's to 4 thousand instantly, it takes a second even in neutral. Once we add the transmission and the driveshafts and the wheels to the equation it takes even longer for all that power to transfer from the crankshaft through to the wheels. In layman's terms we call this lack of responsiveness "throttle lag."

Further, stock cars straight from the factory aren't designed to take full advantage of their abilities, the manufacturer wants that car to last the owner a long time.
The more we ask from our vehicles, the less reliable they become. Thus the manufacturer may have intentionally not built these Impalas to racing specifications.

Some things that can be done to increase the pedal's responsiveness are to install thicker high performance (8mm Accel or Taylor) spark plug wires.
You may consider replacing the spark plugs at this time, especially if they haven't been done in a long time.
A thin synthetic oil such as 5w-20 will also help reduce friction that may be slowing the engine.
Believe it or not filling each tire to the Max. PSI printed on the sidewall will help as well.
Beyond that a clean air filter, maybe even an aftermarket K&N to help deliver air down the intake faster.

If any one or more of the above isn't there...
The car will lag.
It could even be that the caliper guide pins haven't been lubricated in a long time and the brake pads are mildly 'dragging' on the rotors, for all we know...

Once we're done with the simple stuff unfortunately we're looking at crazy upgrades such as polished intakes and cold air intakes and all sorts of other things that, may be cheaper to reprogram the ECU to a stage 1 or something...

Hope that made sense, what I'm saying is there's probably nothing wrong with the car in that sense.
You want less lag, the first step is always keep up on the maintenance.

The issue with our car happens in neutral as well as in gear. It is almost like a hiccup or like a dead spot around approximately 7-800 rpm's. Once past that point the car accelerates just fine with no issues at all and has plenty of power. No change in efficiency. The car is not displaying any codes and has no stored codes either.

I just changed the plugs last Wednesday to bosch double iridiums, the autolite iridiums I put in the car around 100 thousand miles had a little over 60 thousand miles on them. The autolite plugs at 60 thousand miles did not look too bad. The lfx engine uses coil packs at each cylinder, there are no plug wires. This car has a k&n filter, was just cleaned within the past 5-6000 miles. So the car has had a complete tuneup within the past 5-6000 miles, throttle body cleaned, maf sensor cleaned, 2 treatments of techron injector cleaner.

Prior to this morning my wife has only driven the car a couple times since the plugs were changed, she said the car has not had any more hesitation issues yet. If or when the next time this problem/issue presents, I will just go ahead on and get a new throttle body and replace it.