I have a 93 k1500 4x4 suburban. When the vehicle is cold, and you depress the gas peddle engine will stumble and rpm will actually drop, usually to an idle. If you hold gas pedal down, rpm's will pick up after about 2-3 seconds. Once the engine is warmed up, vehicle runs normally.
TPS voltage is normal when problem occurs,(Have an OTC scanner, can monitor when problem occurs...voltage is normal and varies with gas pedal depression normally) fuel pressure is also normal at 13psi. Vehicle has new spark plugs, cap and rotor...factory GM parts. New fuel pump and fuel filter. Also has new o2 sensor. Any ideas? ECM? Ignition module or coil?

Have you cleaned the fuel injectors? Try a bottle of Sea Foam or another GOOD cleaner.

Here's a reply I made a couple days ago in another thread.

http://www.automotiveforums.com/vbulletin/showthread.php?t=366572

^^ That's the same vehicle as this post :)