Cylinders # 4 5 6

[Piston]

I'm not sure what the deal is here. After changing the spark plugs this weekend I have some concerns with my 98k x5 3.0i.

I am identifying the plugs from the front of the engine to the back. So closest to the firewall is #6.

Moving on plugs #1 #2 #3 look aged but good #4 #5 #6 had oil on the threads. I will take a picture of them later tonight.

Things i probably should disclose to help diagnose: I recently (6 months or so) had my oil separator replaced with the new cold weather version. Things seemed just fine. I do see some smoke in the tailpipes and it increases with RPM's. Also I burn a quart to maybe quart and a half every oil change which is ~4k-5k miles. Let me add this I've been burning oil on this car for a long time.

Oh after the plug swap the car is very responsive and fast.

I'm hoping this is a valve cover gasket but i'm not sure how to test that. I also didn't see a write up to replace the gasket in the how to's.

Any help would be appreciated. Thanks.