Worst thing I did was rather recent... I tried to save money by getting
the S&S headers exhaust instead of the factory exhaust.  It didn't fit
right, the gaskets seemed cheap (I just had to replace them after <1
month) and I ended up spending more money (since I had to get help
putting it on) than I would have if I had coughed up the extra money for
a factory exhaust system.  On top of that, I hear they don't last as
long.  Boy... if there's one thing I could go back and do differently,
I'd order a factory vanagon exhaust.  I'll probably get a chance to do
that in a few years....

Of course, other people's experience with the S&S headers pipes might be
different.  Just my opinion.

-Wes