99 Denali Random Misfire Issue

[Cefus]

So I am at a loss with this one. I am getting random misfires and grey smoke out of the exhaust. I’ve replaced the spider injection, the upper and lower intake manifold gaskets. The fuel pressure regulator. The fuel pump. The o2 sensors. The catalytic converters. The spark plugs and wires. Cap and rotor and the radiator. I’m at a loss for where this misfire is.

 

[GoToGuy]

Get a scanner check for active codes, and inactive. Check what are your sensors telling you. Normal operating or something's malfunctioning.
Why did you replace all the parts? Where the parts for the misfire or did the misfire start after your parts replace?

 

[Cefus]

I got it from my family and it needed a full tune up but already had the misfire and slowly began to have an issue starting. I ran several code readers all coming with the same if I remember correctly p0300 random misfire code and originally it was throwing codes for the o2 sensors before they were replaced. I did research found the lower intake was pulling excessive air and pulled it apart and found the gasket in pieces in places. It seems like it ran better before I sealed that leak and now it’s got a rough idle and blowing grey smoke.