Alright, I am out of ideas. I have a 2006 Silverado 1500 with that garbage 4.3L V-6; ~190,000 miles. For about the past year, I have been replacing this sensor and that sensor trying to chase down periodic, seemingly random misfires and other issues. So far, I have replaced:

MAF
Air Filter
Crankshaft Position Sensor
Camshaft Position Sensor
Temperature Sensor
Throttle Position Sensor
Plugs/Wires
Bad injector
O-ring for "spider"
Fuel pump and filter.

About 3 weeks ago, the truck started running very poorly. I thought it was the recently replaced fuel pump failing. I stopped by Auto Zone and they pulled a code that said the MAF needed replaced, so I bought one right then and replaced it. The truck wouldn't run. I had it towed to the shop. They kept it for about three days and couldn't find anything wrong with it. Truck started and ran fine. It had compression, fuel, and spark. About 10 days after I got the truck back, the CEL came on and the truck began bucking and stuttering. It became very slow to accelerate and I heard periodic backfiring. I returned to Auto Zone and the code indicated a bad cat. I drove it back to work where I have a shop and the truck died and would not start. I removed the cat to see if that was the issue. Still no start and I can smell raw gas. We had a contractor at the shop who said his truck had a similar problem and he replaced the Crankshaft and Camshaft Position Sensors, so I did the same. Still no start and the gas smell persists. I have checked connections and wires and everything looks good. I just don't know what to do anymore.

I need some ideas. I only have one vehicle and this truck being down is putting a heck of a damper on my landscaping side business, making repairs awful hard to manage.

Thanks

 

Your symptoms sound familiar. My Toyota's oil control valve solenoids (OCV) (related to variable valve timing system) were dirty and caused intermittent loss of power and rough idling. From what I remember reading, there's some overlap with this, the Cat, and O2 sensors.
The resistance of the OCVs can be tested (sorry, cant find normal ohm measurement). Cleaned mine with intake cleaner and solved the problem.

Far from definitive but I hope this helps.