after my new things that i added....i feel like i have no power, but i do have a header leak.....i can hear it when i goose it....would that cause a loss of power???

when setting the timing should i disconnect the battery????
If you disconnected the battery with the car running, there's a decent chance you can fry electronics in the car. Definitely don't do that.
Good luck.
Yup. Most people don't believe that because old timers check the alternator this way.