Any help from the experts would be appreciated.
Last year before I stored the car I changed the valve cover gasket and the seals for the spark plugs. I wasn't happy with the way the seals around the plugs sat, but it all went together ok, so I thought?
Car ran fine after I brought it home, but now it has developed a rough running, as if it is running on 5 cylinders. It does it at idle and when at all road speeds.
Could I have screwed something up when I changed the valve cover gasket?
Anyone who could give some advice where to start would be appreciated
Also I have no shop manual, I have heard All Data has on line manuals at a charge of about $40.00 per car. Any input?

 

I ordered new plugs and ignition wires from Lone Star. $265.00 Canadian
Took 30 min to install. Runs better than it ever has
I am sure they were the original wires, but the plugs have been changed.
95,000 miles.