1992 Chevy k1500 5.7L 350 rough start and stumble at speed.

[ironcross]

alright so this is whats happening...
i go out to start my truck in the cold or the warm depending on how long the truck has been sitting and it will rough idle like hell. you can hear the exhaust popping real hard and the RPMs are not stable. now this wont happen after i get to work and go to leave about 7-9 hrs later, but i park the truck over night and it will be like this in the morning. my neighbors hate it because i have a flow master super 40 on it which is loud as hell. then i noticed that at highway speed or even in the city it will all of the sudden stumble and pick itself back up. i need this fixed soon. i have replaced the MAP sensor and since then it still does everything the same and now even gets a SES light sometimes. truck has about 217,000 miles. what else is there to do?

[masterhacker]

First Fuel filter, Plugs, Wires, Cap/Rotor Then if its not fixed Oxygen sensor ignition module, ignition coil, Also check all your vacuum lines, If they are more than 5 years old replace them. If any of the rubber elbows have cracks you can replace them with fuel hose, and replace the rest with vacuum hose (i like silicone). you can check for leaks by wiggling lines where they connect, or spraying carb cleaner around them either way it should change how the engine runs for a second if you have a leak