99 , 114k, All stock.

Replaced plugs and wires with NGK's / copper plugs.
Didnt change anything... What else is typical for this problem?

 

Fuel injectors??

My 1991 stock developed a feeling like it was dragging a safe until 3k-4k and then it felt like it had an extra cylinder as it flew. Ran some SL1 injector cleaner through the fuel system along with a long highway drive and it went away.

 

the problem goes away once the car is fully warm...

still think its the injectors?

 

Not sure about it going away when it's warm but a bottle of injector cleaner wouldn't hurt. I guess it could also be a O2 sensor acting up. With a 99 a coil is also always suspect but since it stops when warmed up and your not getting codes the coil is unlikely.

 

Maintenance. Pull the MAF sensor out and clean it with MAF sensor cleaner. Clean Throttle Body (TB) with TB cleaner. Remove intake manifold and clean it out (they get really dirty, so just do it). I'm assuming you put the correct plugs in and gapped them correctly. I think running premium fuel is a better injector cleaner than most products out there. (I also highly doubt that's where your problem is coming from). Can also clean your 02 sensor.

 

Let the car warm up before driving.

For the cost of one, I'd throw a new O2 sensor in the car. Does it smell like it is running REALLY rich when it is warming up?