[whynotthinkwhynot]

OH, something I didn't think about, may be part of a problem in your car or not. On older cars crud would build up around the spark plug on high mileage heads. When you remove a plug, and then put another plug back in- the crud would get between the new plug and block screwing up your torque. I used to have to take a 1/2 extension, wrap a shop towel around it, and shove it in the spark plug socket and twist it around until I cleaned all the crud out from around the plug socket.

I don't know if that's your problem, but it might not hurt to either try cleaning, or shine a flashlight around in there to see if you have crud buildup.