How do reduce the sourness of pasta cooked with peppers?
Most likely the peppers. Jalapeño &amp; Banana Peppers are usually canned as a pickle, so yes, it is sour.  You added some of the pickle liquid as well; I feel your dissatisfaction with the results. =-)

I love peppers (pickled or otherwise) in noodles. What I do to cut down on the sourness is drain the peppers of it's liquid and rinse with cold water once.  Then the results will be much more delicious.