CHEVROLET BLAZER COMPUTER NO COMMUNICATION

I Have No Communication With The Vehicles Ecm I Have Even Changed It Out I Have Also Checked All The Fuses Still I Have No Communication...

Changed The Fuel Pump And It Starts And Dies Out Immediately So I Scanned The Computer Box To See If Any Codes But Shows Error Or No Link

Rough Take Off Backfired Through Intake, Struggles Up Hill, Ok During Mid Range, Lack Of Performance 2000 Chevy Blazer. No Check Light...