I own a 2007 Charger with a SRT8 Hemi 6.1.  Approximatley 6 months after the purchase of the car the engine developed what I call a flat spot in exceleration.  This under normal driving conditions in town and not on highway.  It happens when you put on the gas leaving the light.  I have had it to 3 dealerships and nobody can fix it.  I have been told it could be bad gas, that I should drive it like a race car every day, and it could be the rear gears in the car?  Has anybody had this same issue?  If so what was done to correct the problem.  I am at my wits end with this problem as no dealership can find the problem but all admit that it is not right.  Please help if you can. Thanks  

Is it only in first gear? is it slipping gears? or does it seem like gas isn't getting to the engine? sounds wierd...  

Yes, it is in first gear.  The Transmission has been checked and does not slip gears.  The only way I can explain it is that in the older cars when the vehicle had a bad spark plug and you would get that flat spot or hesitation when excelerating from the light.  I have also had them pull the plugs and check them.  They say everything is fine with the plugs.  They have gone through the fuel injectors and they say those are fine also.  The first six months I owned the car there was no hesitation now there is one and they (the dealerships) have driven the car and admit that it is not right.  It only happens when leaving the light.  You can put it on the highway and it is fine.  It only happens when you drive the car under normal conditions leaving the light or taking off from a stopped position.  It hesitates uphon acceleration up to 3000 rpm's.  Flat spot in powerband at low rpm's.
The last diagnistic they gave was:  "Vehicle is operating as designed due to the gearing in the rear differential.  Vehicle is designed for top end performance and will have hesitation/lag at low speed."  Why would it take six months to develope the extreme hesitation if it is the gearing?  I agree with you it is weird!  

I've had a couple new vehicles now that have done something I never noticed before in my vehicles - they get better mileage as they get older and terrible mileage when they still have the dealer smell.  Here is the explanation and it might explain for you as well.  
When a vehicle is new it is not fully broken in - and given the latest tight tolerances they get worse mileage until they fully break in..... not a defect, actually a benefit since the cars last longer.  Okay, here's my point - is it possible that your car is fully "broken in" and is accelerating better then when you first drove it off the lot - meaning, you have better acceleration now then before.  Have you actually timed the car to see if your ets are lower higher or the same?  Perception is everything in your stated problem.  If that is the case, then getting lower (higher numerically) gears would be your only way of offseting this situation.
If it's not the problem, I'll refund all the money you paid for my two cents worth.    

I say it has something to do with fuel delivery, A weak pump or a bad filter. Sounds like when the weight or the fuel is tossed to the rear of the tank the pump for some reason or another is having a hard time keeping up with the pounds per square inch it was designed to deliver. Could be a lower voltage going to the pump also. Seeing how the car is idling and in gear which means an even lower idle hence a lower voltage. Hope this helps in finding the problem. Try bringing the rpm's up while sitting there (kinda like power breaking but not breaking the grip of the tires) and then see if it launches any better without the flat spot. If that's not it then have a fuel pressure test done on your system by someone other then the dealers. They may be avoiding a costly replacement.  

This car has an electronic throttle. It also has an electronic stability program (ESP) that can control the engine power.  So if the ESP sees a wheel spin or thinks there is a wheel spin (bad sensor at wheel perhaps) it will detune the engine to correct the spin.  Does it do it with ESP off?