thundering noise when pressing accelerator

Hi,

I have 2001 i30 with about 70k miles and all the services done regularly. Since yesterday evening whenever i press accelerator car make very big thundering noise and when i take my feet off the accelerator the sound goes away and this is irrespective of whether i hit the accelerator at 20mph or 70mph. There is no check engine light and RPM looks normal while driving, What can be the possible issue for this noise?

Thanks
--rubs

Exhaust manifold /pipe seal(s) leaking and/or support broken (pipe touches chassis).

"...feet off the accelerator the sound goes away"
- pressure is up while accel, drops to minimum at idle. Sound=airpressurepulse.
- engine angle changes and piping bends/moves, causing loosened/broken joint(s)s to pry open

Do crawl around to pinpoint, see/hear/feelbyhand the leak while smbdy exercises the gas pedal