2013 1.6vti Misfires

[Mde80]

I had the rocker cover gasket replaced. A few days later, accelerating up a hill, the car started juddering and the engine light came on.
The codes read P0313 low fuel misfire. P1336 crankshaft position. P1340 c4 misfire. P1339 c3 misfire.
The low fuel misfire seems obvious as I was very low on fuel and zooming up a hill. oops!
The crank sensor error freaked me out a bit as my previous car threw its belt on the same hill. After clearing codes, it hasn't happened again.
A couple of days later, I was caning it up a different hill and it started spluttering again. I reset the codes and all was good.. until I had to go up the same hill, where it gave up at the same place. The presence of hills might just be coincidence but I started to wonder about the fuel pump/filter. The scan showed misfire on 3 so I thought I'd change the plugs and grab a coil pack to test.
On changing the plugs found the tube on 3 full of oil. I told the garage and the guy (who hadn't worked on the car before) said that I need a new rocker gasket. I explained that they changed it a week ago and he went to get the boss. They said they'd look into it and if it was misfitted they would sort it. A week or so passes and I'm told that they've fixed the oil issue but still a misfire on 4. I explain the it was previously missing on 3 (the very oily one that I replaced the coil on.) Garageman says that they've swapped coil packs and it still misfires on 4 and needs further investigation.
Apologies for the essay. Any thoughts?

[mickthemaverick]

Sounds like oil contamination in both cyclinders to me.

[PaulC5]

Citroen tend to number cylinders from the gear box end so cylinder 4 is at the timing chain end on your car.