I have a 97 Dodge Caravan with a 3.0 litre engine.  I recently had some
stalling and re-starting problems that were traced to the PCM controller,
which was eventually replaced.

Also, within the past six months, the muffler and resonator were replaced at
a country garage that used after-market parts.

Now, when I first start the vehicle it runs like a charm but after warming
up it sometimes sounds like there is a huge hole in the exhaust.  Sounds
good at idle but under load it becomes loud.  When the exhaust noise starts,
the engine appears to be running fine with no hesitation, coughing or
stalling.  If I make a short stop (to get gas, for example) it often sounds
just fine after getting on the road again.

As part of the diagnosing of the PCM problem, the compression was checked
and found to be ok.

When it is idling it seems fine and therefore hard to check for exhaust
leaks but from what I could tell there weren't any obvious holes or any
leaks around the joints.  The emissions were checked and were excellent.

Before I declare the muffler and resonator to be a piece of junk, are there
any other thoughts that anyone has.  Are there any sensors for example that
might cause this?

Thanks for all thoughts.