I own a 2002 GMC Sierra 3/4 ton. I have cleaned the injectors, changed fuel filter, changed oil and filter, replaced tires, but she is still fluttering and then dyeing. The RPM's drop and it feels like I am not getting gas to where it needs to be. I pump the gas petal and sometimes it stops it from dyeing. What is wrong with my girl??

Oil Change & Filter
Transmission Fluid Change & Filter
Fuel filter
Air Filter
Plugs, wires/boots, cap & rotor if applicable
Clean the MAF sensor with MAF spray.
Clean any debris out of the air intake box.
Run some seafoam in the fuel to clean injectors.
Check tires & pressures.

TUNE-UP, SPARK PLUGS, WIRES, AIR & FUEL FILTERS, FUEL INJECTOR CLEANER IN TANK, ALSO REPLACE PCV VALVE, & MOST IMPORTANT, REPLACE EGR VALVE, IT GETS TOTALLY CLOGED UP, YOUR ENGINE IS KNOWN FOR THAT. I HAVE A GNC 2500, 3/4 TON. SEEN IT ALL. CHANGE YOUR DISTRIBUTOR CAP & ROTOR ALSO. JUST DO IT !!!!!!!!!!!

best way to get good fuel economy. buy a smaller vehicle. (just kidding) if you want to get the best fuel economy your truck can get there are a few simple things to do.
first. do a tune up. replace your plugs, wires, and if you engine has a cap and rotor replace these too. if your truck is coil driven to the plugs. make sure your coils contact points are clean. you can do this with a small soft wire brush. DONT use sandpaper or a hard wire brush as they scratche the surface on the coil contact badly and leave places for water to condensate and create corrosion.
next replace your air filter this allows your engine to get the best air to fuel mix by making sure the engine gets the proper airflow.
third. make sure your tires are inflated to within 2 psi of the max the tire will hold. having a properly inflated tire makes the vehicle roll easier and cuts down the amount of fuel required to get it moving and keep it moving. it also saves on tire wear at the same time.
while doing this you might want to check your oil and replace the oil and filter if it needs it.
as far as aftermarket mods that supposedly increase your fuel economy. there are none that give you that miracle increase in your fuel mileage.
you might be able to get better fuel economy by opening your exhaust a little by going to a slightly bigger exhaust size coming off the engine and going all the way back. no more than 20% bigger than your stock exhaust. this allows the exhaust to escape the engine more easily and allows it to work more efficiently.
i actually picked up about 3/4 to 1 mpg more economy on my truck by going from 2 1/2 exhaust to 2 3/4

Check the oil,smell the oil,to see if there is a gas smell to it,if so,the injector spider,has a broken injector line.The intake will have to be removed to replace the injector.

Did you try a 3 stage injector cleaner and intake snake. Cleans throttlebody of carbon. I had to push a truck into the shop because it would barly idle did all that and it did wonders. Guy squaked the tires leaving because of the power that was given back. Also high mileage oil, Full synthetic on older motors can cause pan gasket sweats.

Replace the pickup coil in the distributor,this pulsates the injectors.

New fuel filter, Spark Plugs & Wires, New air filter.
Tires at max cold psi.
Use a bottle of injector cleaner and change oil every 3k

the intake manifold on them motor where cast bad and lots of them end up getting little tiny holes in the i have change lots of them for that prob also fuel regulaters leaking

basically, no matter what contaminated it, you gotta clean it out. even water. worst case is drop the tank, empty and flush with clean fuel. replace tank, replace all filters, disconnect the fuel line at the engine end and turn on and flush with clean fuel... and hopefully your fuel injectors survived. if just water, they will probably be fine. if something like sugar was dumped in your tank, that is not fine. change your oil and oil filter too. and cross your fingers.. in fact change your oil again after one day. and cross your fingers again... maybe even a third time... and you know what to do next ... sugar is bad bad bad for engines. if it got in the crank bearings cam bearings, into the push rods, lifters, on and on and on, its like pouring sand inside the engine.

It could be electric fuel pump stall. The pump isn't pumping fuel fast enough. This model may have a inline fuel filter before the fuel pump as well that might need replacing.