Review on ACDelco D521C Ignition System: Original Equipment for Optimal Performance by Jyothish Pillai

Looked like the original, the assembly is simple. The local auto parts store wanted almost twice as much for the Duralast. Saved the kit for 2 days of waiting and got an OEM part. Check Engine illuminates when code 0300 is issued (random misfire). The car gave frequent misfires at all speeds, but mostly under heavy loads. The odd thing was that only 1 cylinder looked bad on the original spool so 0304 should have been fitted instead. I was glad that the new coil pack solved the problem.