rotor trim

I apoligise in advance, I may explain this shit. We have a methanol powered 13b running 12 injectors. We do a power run, the car makes the power, and the AFR's are right where we want them, but when you pull the plugs the rear rotor L2 physically to look at is lean. Now if we apply a lets say 8% rotor trim to the rear rotor I would expect the AFR's to go rich, but the close loop is keeping it on target. My question is for the motec m1 to keep the AFR on target, will it subtrack fuel from both rotor one and rotor two to keep it on target? If it does go rich essientally running the good front rotor lean?

If you've got a trim set biasing a rotor and then close loop needs to pull or push more or less fuel it will be a gross percentage of fuel squirted, meaning both rotors will be affected. With regards to variances between front and rear rotors the rear rotor will always run hotter, even with aftermarket and equal length manifolds as theres no way around the stock water path unless you tap in new water lines right over where the combustion chamber would be.

Why don't you add your trim to the rear, and also change your fuel mixture aim to match the resulting lambda readings (open loop). Then any adjustment will be to keep you on your new target.

so Add trim to the rear until the plugs match in open loop and take the afr’s from that change and enter into aim table?

Sure, though I'd opt for fine tuning with EGTs and live data over reading plugs.