I've been needing help with my 5.0, it starts and runs but there's a huge power loss. The motor shakes tremendously when the gas is applied and it goes over 2.5k rpms it goes back to normal, my harmonic balancer has a lot of play also, cars is mostly stock has a msd distributor which was put on by old owner and he claims he did something with the timing also. Stock headers and exhaust but has dumps. Really need help getting it back to full potential. Thanks guys !