Are you sure the pump you got was good? I mean, did you have the same pressure before *and* after the change? Sometimes replacement parts aren't good either.
But my gut tells me you have other, bigger issues. Was the car ragged on at some point? If damage hasn't been done yet, putting in new con rod bearings isn't that bad of a job. On most cars, it can be done with the motor still in the car (from below).
<img src='http://home.comcast.net/~eric_d_johnson/sig_pic.jpg' border='0' alt='user posted image' />