Its kinda hard to explain what Im getting at lol....if the 25ECU is batch fire and using a Sequential ecu, and have to swap a pin so all 6 injectors fire instead of 5 or 4 or what ever the case may be, is that the wiring may not quite be right.
As an example on the EF falcon 4L they run batch injection and wasted spark...runs perfectly fine as standard as the intake valves are closed when the injector and wasted spark fires on the exhaust stroke...when you fit larger cams with more over lap the valve is slightly open and fresh fuel gets into the chamber + the wasted spark was igniting the fuel as it entered the chamber with the intake valve open, only happened at low load/idle though, but the cars never ran right even at WOT
Only option was to run a funky cam profile or fit an ECU with 6 injector drivers.
Thats my basis for thinking what I'm thinking about the funny little missfire that some guys get.
I maybe completely wrong in this instance, especially with the RBs running coil on plug...but it maybe fuel is being squirted at the wrong time into the chamber on 1 cylinder.
Not that its really important as most owners dont report problems....It could also be that there are a couple of different types of ECU's...I know RB25's have 2 types maybe Silvertop RB20s are the same??