Okay, after about 2 months of not driving my Z4 because it started to spunder/rough idle, I took it out this holiday weekend to check out, and the code I got back was P0305, here is what I found on the net:

It seems to say that there are generally 4 possibilities in case of a P0305 (or any P030x) cylinder misfire:

1. - sparkplugs
2. - plug wires/boots
3. - ignition coil
4. - fuel injector

Now, from reading from other forums, #1 it seems this is very common, #2 it a game of trail and error finding out what could be the cause, spark, wires, coils etc... I am just wondering if anyone else had this problem before and how did you fix it?