Low idle

Hello guys. I have an idle problem with my 4.2. Once warm the idle drops to about 5-600rpm and you can feel the car miss. I plugged it in and it said cylinders 4 & 8 misfire and idle control system maximum limit reached? I've cahnged 1 coilpack and will change the other but does the idle limit mean anything else?

[A8 3.7]

Hi had a similar problem on my 3.7 check the breather pipe at the back of the engine comes from up the centre of the V to the throttle body rubber air inlet if the pipe perishes it can cause a misfire plus the idle control valve tries to correct the idle so sometimes the idle can be erratic and the engine cuts out. If it is that the pipe is approx £40 odd. There is another pipe on the passenger side which goes to the cam cover could also be worth checking.
Hope this helps

Thanks for the info A8 3.7!! I'll have a look!