Missing at 3000rpms

If you have an MSD box with a rev limiter check the pill. I've seen guys have a bad 7000 pill that would activate at a lower rpm. OR check the fuel VOLUME. See how long it takes to fill a one gallon jug from the pressure side if your fuel pump (if electric). Wish I could remember how long it was suppose to take. I'm sure someone here knows. OR go with the valve spring thing.