The other day I was driving my ep around. A very rough and loud vibration suddenly started right after a heavy acceleration through first and second gear. Whole car is vibrating horrendously. After diagnosis, I replaced a couple worn out bushings on my innovative mounts, and replaced the header which had a failed weld where the donut gasket sits. Vibration and loud engine sound is still there. Exhaust is not rubbing or leaking. Vibration happens in neutral and while driving. Noise Almost sounds like I'm driving with an open header

Any other ideas on what to check?
Please help, Gotta get this fixed.