Multiple issues needing addressed
 

I have a 2001 Monte LS 3.4.

1. While driving mainting speed between 30-40 mph, it feels and sounds like the car is reving itself. The rpm needle is going up and down in between 2-3,000 rpms.

2. 6 months ago my car was misfiring so I changed the spark plug wires (AC Delco) and the issued was fixed. Now it starting to misfire again. I'm hoping its just the spark plugs that need to be changed.

Opinions and all possibilities of what the above issues may be, would be appreciated. Thank you.

The misfire could be your coil packs try them if plugs don't work, as for the rpms I'm not entirely sure but it could be a bad injector.

There is a chance you could have another bad plug wire, I have bought brand new packs in the past and after about 2 weeks they have failed. Could also be a bad coil pack.

The surging could be your Throttle position sensor, MAF (prob not as it would throw a code), gas issue, as in not getting the fuel properly, could be related to your coils if they are bad. There are numerous culprits that it could be causing the problem, it could also be your transmission as sometimes the shift solenoid sticks causing a similar issue.

Then it might also be your egr valve, I had mine go and there was a surging with the motor that was happening as well. But it did throw a code