If there's response by swapping the leads over (within one oil pack) then analysis of why that could happen may give answer.
There's specific performance in the condenser relating to this (if the original system is in place) with it's ability to fire the mixture.
The opposite ends of the coil have slightly different spark characteristics, with also the condition in cylinder from the live one to the wasted spark one maybe causing a bias to disadvantage the live cylinder on compression and give a shift in performance to that cylinder.
Swapping the leads checks for that, also the insulation of the HT too.
Thanks. the leads on my bike are very stiff. I’ve remade the cap connections but I’m not very happy with them. Definitely thinking of doing the Ash fix. On the other hand it starts well and has no high Rev mis fires which makes me think ignition is ok. I can live with the slight tendency to idle foul and my air screws are out more than 1.5 turns from memory running on shell e5. I’ve improved no 1 cylinder running cool by installing #35 pilot jet and overall the bike runs very well.