Trying to troubleshoot but so far no luck. Checked all plugs and no problems there. Also tested coils and batteryl cables/connections. I have uploaded a video to youtube linked below:

http://www.youtube.com/watch?v=KZpZBwq_VoY

Any input would be appreciated.

Let'* see here, we have a couple writeups on these...

P0300
https://www.gmforum.com/showthread.p...ighlight=p0300

P0171
https://www.gmforum.com/showthread.p...ighlight=p0171

Give those 2 threads a read through and if you have any further questions, give a holler!

P0300 is nothing to worry about, that'* random misfire and is caused by what ever is causing the P0171. There'* a reason why P0171 is the first OBD code I did a write up on. It'* the most common and it'* a major pain at times. follow the write up and check everything. Vacuum leaks are what you will be looking for. Remember, there are vacuum lines on your HVAC system, so check those as well.

Agreed, find the reason for P0171 and you should fix the misfire. That'* usually a pretty bad vacuum leak to cause a misfire BTW.

Has any work been done to the car in the last 3-6 months?

Still checking for the vacuum leak, no luck so far. I did have the intake manifold gaskets and valve cover gaskets replaced by a local shop in October. Also they replaced the water pump and new plugs/wires.

Be sure to check for leaks by the injectors. The O rings can leak. Spray everything with carb cleaner.

It'* a pain to get at, most likely though ... it'* your EGR to LIM tube.

To check it, skip the carb cleaner, skip the everything and go to removing for a visual inspection. Yes, it'* a little of a pain to get the LIM bolt holding it.

13mm bolt at the LIM, 13mm nut at the EGR. Once you sneak it out, pull back the part that holds it to the LIM and hold the tube up to the light. I can nearly put money on it having a crack. Hit a junkyard for a new one. I think GM wants your first born for a new one.

If that'* the case, I think I have 2 of them on the shelf

Good to know, I think I'm out at the moment. And there'* 4-5 EGR'* with pedestals sitting here if that says how many I find in bad shape.

I bought a new one 2 years ago. No longer have a EGR on my car.