We present experiments showing a significantly increased FIR photosensitivity of a high-mobility two-dimensional electron gas when transport in the quantum Hall regime is non-local, i.e. when scattering between adjacent edge channels is suppressed on macroscopic length scales. The resonant absorption under cyclotron resonance conditions enhances interedge channel scattering processes leading to a huge resistance maximum in the longitudinal resistance and to the suppression of the non- local resistance.