Well first i have a 2003 monte carlo ss this morning I go ahead and start car and it had trouble starting like it would start and spudder and stayed running then drove it down street wouldn't let me go past 20mph I park it it dies then try to start it up it Shudders in park and stalls I need help with this thanks

 

Wow that's always a pain. How many miles? engine?

First thing I would check is the Vacuum lines to make sure there are no leaks or that one has popped off.
There is one that runs from the back of the engine manifold to the fire wall could be a 3/8" hose, that may have come loose.

If you have not found any vac leaks broken hoses etc.
2nd it could also be a plugged fuel filter as well change those out every 30K or sooner. use a good fuel injector cleaner.

3rd have you checked the Air filter recently, put a new one in every 5K they're cheap. engine has to breath.

It could be the Catalytic Converter is plugged. or the exhaust pipe has been smashed or crimped. or something is in it.
good luck