S4 misfire diagnosis?

[RACK]

So yesterday managed to do a few jobs on the S4, got inlet flapper actuator kit put on, valley pan gasket, oil filter o-rings, check valves and oil jet and pcv valve and sealed the rocker cover leak up

With the inlet off I looked down and all the valves were very clean, no soot or bulid up
All set up and running spot on

Now the problem is, I bought the car with an intermittent misfire, stupid I know but hey, the mistake is made now.
I've got misfire codes on cyclinders 1 and 3, last night I swapped the plugs and coil packs round yet still the same faults on 1 and 3
Cleared them and it was fine, was actually the fastest/quickest it's been.

This morning the idle went a bit rough then the cel light came on, didn't flash as it was solid. It still drives spot on.
Took it to my mech to check the codes and again 1 and 3 cylinders misfire

Kinda ruled out the chain tensioners for now as they're quiet and no codes have come up regarding it.

My thinking at the min is pointing to the injector loom, wire connector to the injectors, the injectors themselves or a cracked seal on them, also read that the pre-cat/cats could be blocked, which could be possible as the previous owner hardly drove it and when I got it a lot of carbon came out of the back after some hard driving, this has stopped now

Does anyone have any ideas?

 

[Paul @ Unit 9 Remaps]

Sure it isn't showing a lambda sensor' could also be a pre cat, had that on my old b6 3.0 v6 petrol,

 

[RACK]

There was no code coming up at all for the lambda mate, I've read a post or 2 saying that the precats can mess up and clog the cat givin the misfire code though, but only things that showed up were misfire on 1 and 3

I've ordered 2 new injector connectors to see if it's those that are knackered.
After that I'll have to check the wires.
Kinda at my wits end with it

 

[RACK]

Another point to make, the fault only comes up when the car is idling, when driving nothing appears and it still pulls hard but if left to idle it can sometimes start to shake a bit.