blah tasting sourdough

You'd need to provide details on how you created your starter, how you're maintaining it, and most importantly, how you made the loaf, before we can even wager a guess. :)

There are a LOT of things that can impact the sourness of sourdough bread.

The first one is a matter of expectations.  Most people haven't actually eaten REAL sourdough bread.  Look at the label on the stuff you brought home.  Does it have yeast in it?  Sourdough shouldn't have bakers yeast in it.  How about sourdough?  Often sourdough isn't listed, because there isn't any in the bread.  Instead, you find lactic acid, acetic acid and fumaric acid.  While sourdough has the first two in it, it is created naturally not added to the dough explicitly.  And it does not have fumaric acid in it.  Adding these chemicals allows the bakery to make what a food scientist thinks sourdough should taste like.  And quite often the food scientist has never had real sourdough bread.  It's hard for nature to compete with an idiot with a chemistry set.

Once we get in tune with realistic expectations (and for all I know, you have had real sourdough and are trying for reality), it's time to look at what controls sour.

In general, it is better to use less starter and have a long rise time.  Two cups is a lot of starter.  In "World Sourdoughs from Antiquity" Dr. Ed Wood has three variations on a San Francisco style Sourdough recipe.  He makes the same bread with 1/4 cup of starter and a 16 hour rise, a cup of starter and a 4 hour rise and 2 cups of starter and about a 2 hour rise.  Less starter and a longer rise yield a much more sour bread.

Some people seem to think adding sourdough starter will change the taste the way that adding cinnamon or chocolate would.  And this isn't at all the case.  Sourdough flavors develop through fermentation, or the rise process.  Some people suggest adding soured sourdough starter to dough; that is starter that has been allowed to work a long time until it has a strong sour taste.  However, this tends to add unpleasant off-flavors and the soured starter will give a very impaired rise.  The best bet is to add a fresh starter.  I like to feed my starter no less than twice a day while it's at room temperature.  I also make sure that the starter is active, and can double it's size between feedings,  I like to use it between the time the starter reaches a peak and when it starts to fall.  

The temperature of the dough/rise is also a key issue.  Craig Ponsford commented that he didn't think you can make a sour sourdough without a long retardation.  Retarding dough is letting the dough rise a long time at a low temperature.  Too many people think that means letting the bread rise in the refrigerator.  However, most refrigerators are too cold to do that effectively.  You want something like 55 to 65F.  Most refrigerators are around 33 to 38F.  Using a freezer with an external thermostat is an option for some people.  Get a used chest freezer through an ad paper, add a brewers thermostat and you're good to go.

Some people go the other way and suggest an elevated temperature.  You don't want to go much above 95F.  However, the goal with in both the reduced and elevated temperature approaches is the same.  Find a temperature at which the bacteria is more active than the yeast.  This leads to more time to develop flavor before a getting a full rise.  A higher temperature can lead to a shorter rise time. 

Next, the amount of mineral, or ash, content in the flour has a profound impact on the sourness of the bread.  More is better.  Look at your bread labels and check the amount of ash content.  If the sacks of flour doesn't mention ash content, check the miller's web site.  Whole grain flour has more ash content than white flours, so adding a shot of whole wheat or rye flour to the dough can help.

Those are the bigger issues...... hope my comments help,

Mike