After changing out the driver's side, I moved on to the passenger side. This is when I remembered that there are torque spec's for P car spark plugs which I had forgotten about! I have changed dozens (hundreds?) of spark plugs but this is the first time on a P car. I typically tighten them "to feel" but, when I did the 22 ft lbs on a couple on the right side, it felt like I was over tightening. I went back and loosened two of those and they were not hard to move (just like the factory ones I replaced on the driver's side). Now I'm wondering if I didn't tighten the driver's enough and should go back in and redo those? They're probably at about 20 lbs.

 

generally, spark plugs should be tightened enough to crush the washers. If you apply anti-seize there is a possibility of over tightening as there is less friction

I would suggest using a torque wrench

 

You might have felt the tightening of the crush washer whcih might feel like you are stretching the threads.

Its a 14 mm x 1.25 thread and torques which based on that are:
Bosch: 15-30 Nm (11-22 lbf.ft.) or 90° after screwing the spark plug in by hand until it is seated.
Denso & NGK: 25-30 Nm (18-22 lbf.ft).

I apply a very thin coat of antiseize and use the lowest number. I've never had an issue in 45+ years.

I'd attach the BOSCH pdf, but for some silly reason the RL site comes back with "This AI image has the incorrect file extension", yet according to the list, a pdf is allowed. Hey, its a computer, more unreliable than the worst car.

 

You said you tightened a couple on the right side to 22lbs so apparently you have a torque wrench. And you have changed a lot of plugs so surely you are familiar with that crush washer feeling. I think you are overthinking and second guessing yourself. Torque them all to 22. What I would never want to do is to complete a plug installation with a loosening movement instead of a tightening movement. Your description makes it sound like that's what you did when you went back and loosened them. You have no way of knowing how tight they are (or how loose) when you do that. Just torque them down to spec and you're done.

 

Trust your instincts. You have changed hundreds of plugs, changing spark plugs on a Porsche is no different than changing spark plugs on a Subaru.

 

I hate that feeling. I even know it's coming and when it loosens up I get a pit in my stomach.