I am having problems with a 1998 3800. I recently had to replace the upper intake manifold and lower intake gasket. After a couple weeks I have developed a random misfire. The idle is rough but the car seems to run fine past about 1200 RPMs and higher speeds. Code p0300 random misfire is consistently coming up and a couple times I have gotten the p0171 bank one too lean code.
I have done the following to it:
1. Cleaned and checked MAF sensor.
2. Replaced MAP sensor and checked PCV valve.
3. Checked for vacuum leaks and sealed all connections on the intake.
4. Changed out plugs and wires.
5. Fuel pressure seems to be appropriate.

Also, i checked the resistance of all the fuel injectors and they are all approximately the same. All of them also seem to be receiving power but with the engine running, when disconnected only 4 change the performance of the engine. When I unplugged the number 1 and number injectors, nothing happened.

Is there a way to test the EGR valve without a bi-directional scanner? Any other ideas? Incidentally, the car is a monte carlo. Thanks.

 

Bad coil pack?