In hot weather, when i'm stuck in slow traffic for more than 5 mins or so, my engine will start to misfire.. idling would be rough as expected. However, after traffic clears, when car starts moving again, the misfire will go away. Misfire goes away faster if I push till high RPMS.

Now, this is also what I have observed on my car (300CE M103):

1. 3 of the spark plugs are wet with motor oil. Changed new ones and happened again.

2. 1 Quart of Oil every 500 miles

I've done a head job about 6000 miles ago and valve stems were replaced but not the guides. Ignition system i.e. cables, coil was also replaced recently.

3. Also, I've noticed power drops a lot in hot weather.

Your valued inputs would be appreciated. Thank you.