My 2014 C63 has started getting consistent P2258 on Cold starts.

I have done a lot of diagnosis already.. but I just can't pinpoint the issue even if it's somewhat reproducible.

Here is what I know so far:
- Code get's raised on a cold start only. I only really get one chance a day for the code to trigger
- Codes are: P2258 - AIR System Control A Circuit High, 1065 - Secondary air valve 1 has a short circuit to positive
- I use an iCarSoft V2 to read the codes, and monitor switching valve/air pump states and parameters
- Air injection system relay replaced
- Air Pump fuse checked and working 40A
- I have shorted the relay connections to test the pump, the pump functions ok
- Replaced air injection switching valve 1, and swapped air valve 2 with the old one that was replaced for new one. Same error still raises on air valve 1
- I have removed both air injection switching valves and then did a cold start, this gives me appropriate error codes. Secondary air valve 1, secondary air valve 2 has an electrical fault!
- To me, this suggests harnesses and wiring is OK for the air switching valves. It also gives me airflow error codes for both bank 1 and 2. This suggests secondary airflow is good and expected. The system itself could be working just fine.
- I have witnessed the system operating, as follows. After a cold start you see the code get raised. Wait about 2-3 mins of engine idle. The air pump will come on at about 50% speed, and I can see injection valve 1 get opened (iCarSoft). A couple of seconds later, air pump goes to 100% and air valve 2 will open. This state stays for about 5 seconds, and then system seems to turn off and won't turn on again for the day, or however long it may take for all conditions to reset
- I have also got a multimeter onto the air switchover valve connectors. I see constant 8.4v when the ignition is on. The air injection system wont activate though after few mins of idle as it can't detect the air switch valves presumably as I removed these to probe the connectors
- I have a visual check of the air injection valve wiring, and ECU wiring
- Car has only done 19k miles, engine bay is very well kept and clean
- Car has a wavetrac LSD and remap already done before I bought it, I did not see the error for a couple of months of new ownership
- I had the secondary cats removed (common mod on this car, more noise) I can't confirm, but possible after this the issues started. Can't confirm if related or not, this mod is incredibly popular on this car and no ECU tuning or modding is required as the secondary cats don't have lambda sensors
- Code occurs 100% on a cold start. EML is raised after 2 or 3 occurrences of the code without erasing
- I haven't tested any of the metal vacuum valves, I assume the system is operating correctly from my diagnosis so far above I am completely stumped by this, completely non-intrusive but annoying issue as it triggers the EML!

Any advice welcome I am ready to do further diagnosis. At this time, I'm thinking of monitoring the voltage of the air valves DURING a cold start to see if they are both consistent, as the code only triggers for valve 1 and not 2.