Sounds like a bad master cylinder, check for any signs of leaking on the underside of the cylinder. I'm surprised your abs still works!! This is the first lumina i've came across that still has a functioning abs for some time! My wheel sensors gave out about 115K and so i disconnected the ABS system and I've been driving on conventional brakes for 100K now. here in minnesota the salt eats up the sensors pretty bad~! But anyways, you have all new brakes at the wheels, my guess is a bad master cylinder.