1990 Lumina missing/misfire

I have a 1990 Chevy Ilumina. I haven't had a problem with this car at all until recently. The car has started missing. I have replaced all of the coils with new ones, I have changed the plugs and plug wires and I still have the same problem. I can be driving along and all of the sudden the car starts missing. I can keep driving the car as long as I give it extra gas. It doesn't matter if I am in traffic or if I'm driving down the freeway or if the car is hot or cold or if it is wet or dry. I am not getting any warning lights on the dash when this happens. Does anyone have any suggestions what the problem may be and how to solve it? Any help would be greatly appreciated!

Thanks,
kdeville

Is It A 4 Banger? I've Had The Same Trouble; I Am Preparing To Swap The Throttle Body On My '90 Lumina 2.5l. It Has Been To Several Mechanics And Had Every Ignition Part Possible Replaced, To No Avail. It Was Finally Properly Tested, And Determined That The Fuel Injector And Fuel Pressure Regulator Were Faulty.
Have Those Tested, And Also Check The Egr Valve And Passages.