How bad is this?

 

Pretty normal carbon build up on the intake plenum from what I have seen, I assume over 100-150k miles (?). When I did my plenum spacer my plenum looked about the same, except the PCV valley wasn't as dark. Maybe a missed an oil change or two over its life. Oil catch can will help prevent that buildup in the future. Are you using synthetic oil?
Those spark plugs look like its running pretty rich, might be worth investigating why. Those look like copper plugs too btw, you want iridiums or laser platinum is what the OE is. Coppers are good, they just don't last nearly as long as the aforementioned.

 

I concur. I pulled mine off a few months ago at 136k miles and my plenum wasn't quite that dark, but still had more buildup than I was expecting. I've used synthetic since new and never went more than 4.5k miles in between, not sure if that helped any.

Those plugs though, wow.

 

Intake plenum is pretty common for a high oil consumption VQ. Those plugs as others have mentioned are the wrong plugs. However the condition is pretty fouled, looks like your rings are possibly at the end of it's life due to that much cake on them.

The oil on all the threads of the plugs looks like you're valve covers are probably leaking as well.

I recommend doing a compression test to see if there's any life left in that motor.