Car was running great and slowly developed a miss under load . Its starts at about 3400 rpm,seems to be one cylinder, plugs look good ,valve lash looks good .Here's the kicker I'm running a early 90s vertex mag and a 650 holley.As I'm typing I think I'll check the fuel filter. But anyhow I want to rule out the mag any ideas? I'm going to put it back together and put a thermal light on each header tube to isolate the cylinder.