Clogged cats are a frequent problem on
cars of this vintage. One quick test you can
make is to remove the air cleaner start the
engine and standing by the drivers fender
rev the engine and listen. If you have a
clogged cat you will here a distinctive snapping through the intake. The noise is
actually caused by the engine trying to
exaust through the intake on valve overlap.
Keep in mind if you have a clogged cat it
was most likly caused by bad valve guides
so the clogged cat is a symptom of an underlying problem.