engines actin up

[camaromanz28]

after changin my gears, i took my car out and i matted it to the floor and had no power at all, so the next day i started on my headers changed the spark plugs which were shit and changed the wires, i got done my headers and my y pipe, i started it up while it was on the jacks and it ran perfect, as soon i as i let it off the jacks and started it up, it started to act up, i took it out and punched it and still had no power, please any help is appreciated

[Dr.Crash]

does it still go through the RPM's? What does it feel like. have you changed anything else?