Exhaust blow!!

hey just a quicky! iv got a 89 cabby and when the car idles it sounds fine and when accelerating softly is also fine but when i give it some stick it blows! im guesing its the manifold/downpipe gasket. its had a new downpipe and c clamps. is this common? weak engine mounts or poorly fitted downpipe? any ideas?

Is it defo the downpipe blowing?

I thought mine was blowing a few weeks ago but turned out to just be the front section.

Ended up getting a full custom built system then.