Hi I have a 2000 bonneville ssei supercharged 3.8 my car keeps choking up when I push on the gas pedel and on the highway on cruise at 80kms keep sputtering and get a black smoke from my exaust and sometimes from a cold start it will not idle I have to keep foot on gas pedel and when it does idle it runs rough goes from 1000rpms to 1500rpms can you plzzzzzzz help me
Ok, first I would look at the plugs and wires. It sounds like it is missfiring with the sputtering.
The black smoke could be from the missfire or it could be from a failed fuel pressure regulator sucking raw fuel into the motor.
The bog could be fuel pressure related or a bad supercharger.
All these could be the reason but you need help from a shop that can touch it and feel the issue and give you a bid.