[buffypanda]

Hi! Some background info..
E92 335i N54.
I have owned the car for 6 months and used it as a daily during the summer with 0 issues.
No plans to drive it during the winter so it has sat in the garage for the last 3 months.
I bought it from a dealer so not much info was passed on from the previous owner other than a list of mods.
Serviced by BMW the day before i put it away for the season which they claim included a thorough check of the condition of all pipes/hoses etc. New spark plugs were included in the service.

Basic mhd stage 2/ stage 2+ mods.
Vrsf downpipes, cobb ic, chargepipe, blowoff vavle, the intake mod every 335 owner does..

I "upgraded" to a vrsf street exhaust myself roughly a month ago.

I have started it 1-2 times a month for various reasons (for the exhaust install/ to make space etc) and let it idle for 10+ ish mins total before turning it off every time. the garage is between 0c and -5c this time of year.

A week ago i started it to drive it up on blocks to be able to lift it up on jack stands and it sounded like it was misfiring so i turned it off after maybe 30s. I got the following codes..
Active codes
29CC - DME: Combustion misfires, several cylinders.
29CE - DME: Combustion misfires, cylinder 2.
29CF - DME: Combustion misfires, cylinder 3.
29D0 - DME: Combustion misfires, cylinder 4.

Shadow codes
29F4 - DME: Catalytic-converter conversion.
29F5 - DME: Catalytic-converter conversion 2.
2AAF - DME: Fuel pump, plausibility.
2F6C - DME: Exhaust-gas flap, activation.

I tried clearing the codes and turned it on later that day with the same codes. Made sure the battery was fully charged yesterday and tried again with the following codes.

29CC - DME: Combustion misfires, several cylinders.
29CF - DME: Combustion misfires, cylinder 3.
29D0 - DME: Combustion misfires, cylinder 4.

Shadow codes
2AAF - DME: Fuel pump, plausibility.
2F6C - DME: Exhaust-gas flap, activation.

Talked to a few friends and they said try revving it gently and see if that helps before looking at the spark plugs etc. Tried starting it today and it sounded like the first time and possibly even more rough.
Still sounded rough after quite a few gentle revs so i turned it off and tried again but now it dies instantly on idle.
Tried checking codes and there are none.

Very limited knowledge so any advice is welcome!