[tpi72blazer]

Once you decide whether you are going to run either a speed density system, or mass air flow, an aftermarket harness such a painless, Howell, or S&P will GREATLY simplify installation. The harness's have the correct recepticals to plug onto the factory GM ones so there is no confusion or possibility of hooking up wrong wires. The ECM itself only has 4 wires to hookup. The type of system you run - speed density or MAF will dictate which sensors you must run. I have not seen an aftermarker harness that comes with sensors. The MAF harnesses are generally more expensive as they have more sensors than a speed density system. You can expect to pay $300 - $350 for a harness, but it will be setup just for your system, making future engine swaps no problem. Do you already have a TPI unit you are thinking about using?