Trying to fix a very slight engine stumble at higher rpm and under load.
1998 4.3. Getting a 0300 code(random misfire) & also EGR, and both o2 sensors showing codes, as well as a vacuum code. Replaced Plugs, wires, cap,rotor, pickup coil, fuel filter and fuel pump recently.

My question is: Is it possible that this misfire/stumble is caused by egr or o2. Or vise versa, the egr and 02 codes are resulting from a misfire.

Thanks in advance.

Trying to fix a very slight engine stumble at higher rpm and under load.
1998 4.3. Getting a 0300 code(random misfire) & also EGR, and both o2 sensors showing codes, as well as a vacuum code. Replaced Plugs, wires, cap,rotor, pickup coil, fuel filter and fuel pump recently.

My question is: Is it possible that this misfire/stumble is caused by egr or o2. Or vise versa, the egr and 02 codes are resulting from a misfire.

Thanks in advance.

I had a similar problem with a V6 Pontiac engine to what you describe.
A faulty EGR valve caused stumbling at a steady pace/speed.

You can remove the valve, and check the pintle for a buildup of carbon.
It may cause the valve to not close properly.

What are all of the the code numbers?
How ramdom is the missfire?
Full or part time miss or dead miss?
What cylinders are missfiring?
A egr valve prblem can give a miss and mess up O2 sensors.
I would check out egr valve for carbon build up and not closing to start with.