i have a 99 tahoe 5.7 vortec gas engine with about 160k on it. this morning i turned the corner by my house and it started to sputter as i pressed the gas pedel. i parked it and got out popped the hood and i smelled a rotten smell like bad eggs. well with that being at three am i went to sleep and got back out there 7 hrs later and now there is no egg smell but obd code p0300 ( random cylinder misfire) came on and i dont know if it is because of the temp outside(about 47 degrees f) but i noticed whit smoke out of the tail pipe and alot of moisture coming from it also. I checked all the plug wires, cap wires, all the vacuum lines all seem tight, no leaky air noise as if a vacuum line was loose. i have been searching online and came down to a bad cat(s) or egr valve. what do you guys suggest? i dont want to just throw money at it as i just moved and am kinda broke lol.

 

Could be bad gas. It's misfiring on #3