I thought the boiler stat control just turned the boiler off sooner, didn't think it reduced gas input.
It's an ideal classic ff boiler, sealed system with grundfos 15/60 pump.
All up stairs radiators have trvs and might be satisfied but all downstairs radiators don't have trvs and the one near the wall stat is fully open.
The boiler is indeed knocking/kettling slightly, don't know if this is air still in system or scale. Due to add some inhibitor. But it still knocks but runs without cutting out on pump speed 3 even when trvs are closed and there is knocking.
Just so noisy and system generates so much air on pump 3.