rx-7 needs ecu help!!

I have a 94 rx-7 rebuilt street ported motor. Problems over boost, and under hard acceleration around 4500or 5k rpm I hear a noise. sounds and feels like it cuts all fuel to the engine for a split second then power comes back up. My mechanic which only works on rotaries says its a fuel problem and I need to add more fuel. We talked about different ecu's and he says I can only use microtech or haltek since I have an automatic tranny. I was looking for a poer fc unit does anyone know what the real problem may be and if I can use a power fc with my automatic. Also anyone selling a fmic and if not the best brand to get? Thanks for your help.