1999 Rodeo LS 4X4 CEL and ODB Code P0303

The wife put gas in her Rodeo a few days ago. The next day it started idling rough, especially when you put it into gear. The Check Engine light started flashing. This has happened before about 6 months ago and I checked the gas cap as I have heard of that causing a CEL. The last time that did the trick, straightened up and by the next day the CEL went away. This time no such luck. Figured might have gotten bad gas so I put some dry gas in. Also bought another gas cap for $5. 2 days later same problem. Took it to Autozone and had them pull the codes. Code P0303 "cylinder 3 misfire" When you drive it the CEL flashes, when it is parked in the driveway running the CEL stays on steady. Looked at some on the posts in this forum and sounds like it may be the Intake Gasket leaking. Guy at Autozone also said it might be a bad coil pack. Any insight would be greatly appreciated.

Thanks,

I had this exact same problem shortly after I got my rodeo. I filled it up with gas and drove for about 15 mins. When I pulled into my spot the truck died before I shut it off. Came back a couple hours later and everytime I put it in park it died. It got worse and would cut out on me in the middle of driving.

Had it looked at and sure enough it was the intake manifold gasket. I could also hear a hissing noise but didnt recognize it because it was like that when I bought it.