Aero causes?
Sorry if my earlier comment caused the thread to stray - I was just wondering about other possible causes for a lack of throttle response. I hadn't thought of the possibility of icing issue. Instead, I was wondering if a slow/sticky variable stator vane actuation system in the engine compressor might be a possible culprit.
Anyway, this is all just speculation in the absence of info. I guess we'll just have to be patient and wait for the results of the investigations to find out what's really going on.