Its missing. HELP!!

[shane72_383]

My truck has had a slight miss for a while now, so i decided to put a timing light on it to get it 100% dead on. Let me tell you first what im running, its a regular old HEI, with an MSD cap and rotor, Accell super coil, and Accell super stock 8mm wires. Ok, so i put the light on it and it does nothing, turns on but doesn't blink? So i figured maybe the wire was to insulated to pick it up, so i put a stock wire on it and tried it again. Still nothing, until i brought it off of idle, then it started to blink but as soon as it dropped below about 2500 it quit blinking. What is the deal? I want to use the light so hopefully i can get rid of the miss but how can i when it wont work. Any help on why its not registering would be appreciated. Thanks