I have been having a problem with an flat spot and stumble at about 2500 RPM's. Car runs fine at other RPM's and problem is not noticable if you run through that range. If you are cruising arond 2500 and try to accelerate car will stumble and than take off. I also noticed that when you are in neutral and and try to hold at 2500 the engine only stay there for a couple of seconds and then fall off to about 1500 and slowly back up to 2500 again. This does not happen when car is cold and that lead me to believe that it was a sensor. So far I have replaced MAF,O2sensor, MAP, and EGR. I have also had injectors serviced and flow tested and replaced fuel pressure reg and fuel pump

I did a conversion from an automatic to manual tran and had the computer reprogramed for the conversion. Could it be that there is a problem with ecm? I have also done a complete tuneup on car. I running out of idea's!

 

Find a cure for your stumble? I also have a stumble around 2250 RPM but runs good in the highr RPMS.

 

I use to have the same problem, but a tune up fixed mine. So if you have done a complete tune up plugs, wires, distributer, and checked the coil out I dont know what it could be. You might want to check for a vacum leak also.