I have a 5th gen Monte 3.1 ltr lately it's been hard to start after its warmed up and it surges at idle.I have replaced the fuel injectors fuel filter don't know if it is maybe a fuel pressure regulator.it's acting like its flooded

 

It may be the fuel pump. A mechanic should be able to tell you if it's flowing @ the correct amount & pressure

 

Possibly the MAF...

 

Depending on the year of the Monte, it *might* not have a MAF (such as my 94 Grand Am with a 3100 did not have a MAF).
At that age could also be some basic maintenance items. Such as when were plugs and wires last changed?

 

A surge at idle could be a vacuum leak. Check all vacuum hose connections and the hoses themselves for splits or cracks.