Mister Bally

Funny, i've only installed Bosch OEM plugs in mine. That's what was installed from the factory. I did have noticed a slightly rough idle as the plugs reach the end of their useful life.

Brozee

Bosch are garbage, they are fine in our cars as were the E3 plugs I had. but overall bosch is junk

Mister Bally

I disagree with you. I have over 160,000 miles on Bosch (oem, not pretty boxed platinum aftermarket stuff) plugs on my A8 and have had no problems with them. Personally, I'd rather have German parts on a German engine versus Japanese.

Brozee

I meant with my general experience across cars, not with this certain one You're a tricky bugger Mr. Bally lol

Mister Bally

I've been called a lot worse! Thanks, I think

Edd W

I'd go with plugs, then coil, then possibly burnt exhaust valve?

VAG-COM!

BOsA6

Well I don't want to be the one with the bad news but might have the correct answer for you with this problem of misfire. I have a 2005 A6 4.2(last year of the MPI) and had the exact problem that your having. Cold start up misfiring and chattering. I did the plugs and coils,and did not fix the problem. I had no leads from anyone so I took it on my own bought the Bentley DVD and dropped the engine. Found a broken timing chain guide and passenger side (bank 1) cam adjuster had gernaded inside it's self! I replaced all parts. Massive job but runs like a brand new car (100000 miles) on the motor. Pull all codes and if you have all misfiring and cam adjuster overadvanced you may have this problem.Attached are just some of the pics I took of the repair.Good luck to you.