The car has done 100,000 miles (i know fairly high maybe, she is a 96 model though, but it was such a lovely car) And my first bmw

This minor issue aside - i really do love the car after only a week of owning her
How will i be able to tell which coils are bad?
The spark plug socket (Number 2 in diagram)

nearest the bulkhead on the right bank of the engine (looking in from front of the car) needed a good pull to get it out when i changed the plugs - was like a plunger :|
Im not a whizz under the bonnet but i'd like to learn about my car
The cable to the idle control valve was slightly out of its holder on the puller so i put it in properly and tightened it up a bit. Seems to tick over fine now, but the vibration is still there up to 2000rpms (standing still and driving) over 2000rpms it seems fine and performance of the car is un-affected :| The vibration feels to come from under the bulkhead/centre console.
*edit* My dad just looked at the cable to the icv - i think something fell off the back of the the little plastic holder mid way along the cable (it sits in the hole on the metal bracket) it fell into the bottom tray..... Car seems to be idling on the little line above 0, think it is about 400 rpm or less?
I got a strong smell of petrol for about 5 seconds last night when i pullled into my driveway after being out in her for about 30 minutes.
I'll check my pipes now.
Cheers for any help guys, it's much appreciated - as i'm quite a noob
