CEL and code for 98 A4 2.8 Tip

My son's 2.8 tip has been displaying a CEL and occasionally flashing. I told him tonight that flashing CEL means shut it off and correct immediately.
He says that when it flashes it usually goes away quickly and is fine for a day or more the repeats.
Tonight we were at a friends place who has a VAG system and we pulled the codes. It was outside in the dark and cold so we didn't get organized enough to write them down but as I remember it the codes were referring to 'misfire on cylinders 4, 5, and 6 (all on drivers side bank).
The engine runs fine and doesn't seem to be going to limp mode.
The timing belt was done with all associated things last spring. The 'optional Audi external oiling system' of the 30 valves was corrected this week but the CEL issue was happening before and continues.
Plugs were recently replaced.
Plug wires are suspect.
He is getting some noise from his cam chains. The CEL seems to be more common when idling so I was thinking that the knock sensor (this engine has one doesn't it?) could be mistaking the chain noise for pre-ignition.
Any guesses?
TonyJ My ride: 98.5 1.8TQM APR (faster than son's 2.8 tip)
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Correction: I had misunderstood my son (That never happens to anyone else does it?) about when the CEL started. Evidently it had only been displayed a few times before having the work done.
He also said today that it seems to occur when idling or when accelerating but goes away at a constant speed.
Tony wrote:

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Coils?
Tony 96 S6

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Yes, we are a bit suspicious of that and probably should test them further.
One theory we are thinking about is the possibility of carbon buildup in the drivers side bank causing pre-ignition. We 'think' this is possible because the friend, who has worked on many audis and did the oil leak fixes for us, says that that bank looked like the timing belt had been installed one tooth off. My son and I did the T belt last spring and were not entirely confident that this had not happened. If it had it seems that there could have been carbon build-up. During the last months the car has thrown an occasional CEL which could be due to mis-timing one one bank. The ECU may have attempted to accommodate this as best it could.
Following the re-timing that was done the other day the ECU may now be a bit confused at the change.
We are thinking about running some SeaFoam in a tank of gas and resetting the ECU bey disconnecting the battery for a while after being sure that we have the radio code following reconnection of the battery.
TonyJ
Tony Curran wrote:

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