I'm trying to fix my friend's 04 Sedan with 66k miles...
To give you all some history of what's been happening, we've been struggling with the P0011 and P0300 codes along with very rough idle, and oil leaking into the spark plug (#6 I believe).

First, we did a fresh oil change with full synthetic and cleared the codes, which helped for about a week, then we replaced all the spark plugs. Didn't fix any problems. Then we replaced the (driver's side) valve cover and gasket. Note that coil pack on #6 was wet from the engine oil leak, and we just cleaned it off.

Codes still remained. Everytime I clear them, P0011 will come back on, and P0300 (random misfire) will come on randomly (no pun intended).

Poured half can of Seafoam in the crankcase and cleared the codes, helped for a day, then P0021 code popped the following day (thinking, Seafoam cleaned the BANK 1 SOLENOID but didn't quite make it to BANK 2.) Poured the rest of the Seafoam, and no help.

Last thing we did, took out the actual Bank 2 solenoid (passenger side, towards front of engine) and cleaned with throttle body cleaner, cleared the codes, and for 3 days no codes and car seems to run a LOT smoothly.

Today, rough idle started again. So rough that the seats are shaking, says my friend. I haven't checked for any codes yet, but I'm assuming it's the same issue (P0011 or P0021, and maybe P0300). Or could there be something still wrong with the wet coil pack?

 

well, never had that problem on a G35, but as of now no ones giving suggestions so ill shoot you mine, i had a 1.8T passat (4cyl) it had a ignition control module, by the airfilter, but below the plastics of the VW sign, there was 4 eng coils, with 4 sparkplugs below each..my car started shaking so bad and it felt like a cylinder shut off, i lost power, and my CEL light was flashing. Ended up checking each coil, (by unplugging while running) to see which one was bad, ended up being the 3rd one right, so i checked sparkplug it was mint, so figured it was the coil, spent 50$ on a new coil same thing, rough idle CEL, ended up being the ignition contorl module, so check out if theres a misfire when you take off individual sparkplugs, or if our vehicles have somethign like a ignition control module that could go faulty..hope i was helpful !