[THEFERMANATOR]

Most misfires are due to the crappy distributor cap design. I use the better one from CARQUEST which is a brass insert model and a blue plastic material(the blue cap with brass inserts is the marine cap). The upgraded MPI kit is a huge improvement over the stock spider injection. Most problems with the spider are rough idle or won't restart right away when hot. Make sure the fuel pressure is good on it(about 45-48 at idle and 55-58 when you stomp on it) as fuel pumps are notorious in the older GM's. Also bad O2 sensors and failed cats are a common cause of misfire codes on the 5.7L with dual cats, and a bad knock sensor can also throw a mis fire code.