damm, thats the same problem i just had on my sr.
my car was running fine until i installed an afc neo. an the same thing tha happen to u happen to me.
i would drive the car, an then out of no were the car will just die out while driving. it wont have any throttle response at all. an then it wouldnt rev over 2k rpms. it will rev to 2k an drop like a freaking 2step. lmao
but i took my car tp jg autoworks an the guy changed some of the setting on the afc an the car hasnt had any problems. he told me it could be the ecu thats bad an running closed loop.
so check ur afc settings if that helps any.
good luck!