Starts then stalls out.
 

I have a 2005 4 door 4 wheel drive Blazer. Every time I start it up it runs but it acts like it wants to stall out. What I mean is the RPM gauge keeps fluctuating up and down and you can hear it under the hood as well does anyone have any ideas what could cause this and how to fix those issues

a big ol' vacuum leak, blown fuel regulator although a big vacuum leak will also cause this. 05's should have an MFI system so you can possibly rule out injectors but its worth visually checking them all if you ever need to take the upper intake off. As i found out just a little bit ago when me and a buddy put two and two together on my rig and got her to fire over finally. if the plenum gasket is original it could have just delaminated from the lower intake and now you've got a nice hole for way too much air to get into.

Thank you so much for the response after me and a buddy of mine completely combed over the engine bay area of the truck we figured out that my mass airflow sensor was disconnected which was what was causing the issue soon as I connected the air flow sensor back up it worked like a dream

sounds like your MAP sensor might be on its way out, with the MAF unplugged it should default to the MAP for AF/R.