I have a '98 Blazer with the 4.3L engine.  For about 1 year it has been
running very rough, especially when it is damp outside and it has sat
overnight.  It usually will run well after about 30 minutes or so.

It has also gotten so bad on 3 occassions that it won't start at all
(cranks but won't fire).  If the ignition module is replaced, it will
then start.  Something appears to be taking out the ignition module.

I have replaced virtually (if not all) every ignition component within
the last 6 months, including plugs, wires, cap, rotor, module, coil and
even the TPS.

It is now dead again, and this time after a shop replaced the module.
It is interesting to note that the mechanic said the base timing was
way too high as well.

Any suggestions are very welcome, as this is getting pretty bad.

The truck has 104K on the clock.

Thanks,

Jeff