Recently I had to remove the front cover on my 1994 3.4 DOHC V6, and
one problem that I had was removing the sprocket that goes for the main
timing belt drive pulley.  It was pressed on, but I could not find an
easy way to remove it.  Turns out you have to tap it for screws and use
a puller, but more on that later.

What you will need:

1.  7/16 thread tap

2.  2 or 3 7/16 bolts (depending on the puller that you use) that have the same thread pitch as the tap.

3.  either a steering wheel puller, or harmonic balancer.

The first thing I would like to point out is that the slots in my
harmonic balancer puller were not large enough for the 7/16 bolts to
fit through, so I used a small grinding wheel on my dremel to bore it
out for them to fit.  I didn't have to do it much, but if you don't
want to do this to your puller, you will need to buy a different one. 
I didn't take out so much that it will cause the puller to weaken any. 
When I did mine, I used a 3 position harmonic balancer puller, but you
can easily do this with a 2 position steering wheel puller.  My
steering wheel puller would need to be bored out as well.

The bolts that I used were 7/16 - 14 and each one was about 3 inches
long.  I just looked at the tap size and got bolts that matched the
thread and pitch, and made sure I had enough length to play with.

The second thing that I would like to point out is that I did this with
the engine OUT OF THE CAR.  I don't know about doing this in the car,
but I would imagine that if you disconnected the lower motor mounts,
and jacked the engine up, you could gain clearance to get the puller in
there.

Onto the sprocket removal.

First of all, gain access to the sprocket.  It will probably be
easiest to tap the holes with the timing belt still on.  That will help
hold things in place.  Once the 2 or 3 holes are tapped (2 holes
straight across from each other, or 3 holes with in equal proportion
from each other), test your bolts to be sure they easily fit in. 

Remove the center bolt that holds the pulley on, remove the timing
belt, and install your puller tool (making sure that it centers
properly, and does not cross thread).

You can then use the puller in the same fashion to remove the
harmonic balancer (tighten the center bolt causing the pulley to pull
outwards).

Once you move it 1/4 - 1/2 inch, it will  easily come out by hand.

Of the 2 pictures that I have included, the first one shows that the
holes are tapped only halfway in (it does not take much force to remove
the pulley, but more than you can do with normal tools). 

The second picture is the pulley out of the car with the balancer still attached.