After leaving the truck un-driven for more than a few days, it takes quite a bit of cranking and cracking and cranking to get it to turn over. And when it finally does turn over, following the cloud of white smoke from the exhaust, it sputters and knocks and idles very rough on the verge of stalling. Letting it run at idle for 15-20 minutes seems to smooth it out enough that it's drivable but it's clearly not performing at its best and gas mileage has been in the 10-12 mpg range (normally 16-18 ).
No OBD codes except for the occasional "PO300 - misfire on multiple cylinders" during rough idle but once cleared that doesn't reoccur.
As the CC is no longer my daily driver and only gets driven short trips on the weekends, I had suspected condensation in the fuel tank. I added sta-bil a few tanks back but, improvement was minimal. I've tried seafoam fuel system cleaner. Replaced the fuel filter. Run a tank of high octane gas through. All have had very minimal and short lived improvement.
I'm suspicious of pre-cat and/or catalytic converter only because of the cloud of white smoke and pungent rotten egg scent immediately after starting and the fact that idle smooths out after warm up.
I've also been suspicious of the ignition system as when I did tune up +/- 25k miles ago, I replaced the stock wires with 7mm wires and they were clearly the weak link in that chain. As I'm getting perilously close to the 100k mark, I'm thinking maybe ignition coil as well... but, if it were an ignition component, would it improve after warm up? a bad wire or coil is a bad wire or coil they don't kinda go a little, do they?
If I can think of any more details, I'll update this but, in the mean time if anyone has any suggestions... I'm all ears

Thanks in advance for any input.