Ok, A while ago I was having some trouble, my blazer was dying everytime i slowed down or stopped, after spending over 200 dollars on a new fuel pump, sending unit and fuel filter I came to realize my EGR valve was jammed open, so i replaced that and it runs alot better...
BUT, as always I have another problem and im not sure if it's related to the EGR or what.
In first gear right before it shifts into second it will drop in RPM 3 to 4 times before it finaly goes. When I had my gas tank off I accidentally snapped off the vent on top, I didnt wanna spend money on a new vent so I just plugged both holes... Could this be why this is happening? Or is it something different entirely?

Thanks

 

OK it looks like i found the source of the problem. My engine light was on so i took it to advance and it said my map sensor is bad and my vehicle speed sensor, so im gonna replace those one at a time and see what happens. Where is the vehicle speed sensor at?

 

on your trans., driver's side, near the tail stock (it's where the speedo cable came out, if you knew where that was).