Thanks all for your input. I adjusted the brakes and that didn't help. I went to get the GM part #4637337 for the upgraded wheel cylinders and none of the parts stores could cross reference the number including GM dealership. I just replaced the rear wheel cylinders with stock and that didn't seem to help either. I do have that proportioning valve and wonder what exactly is it that you can unhook to make it so it is set as if it always has a load??

That valve makes very little difference in anything if any at all. Pretty sure you can count on the brake lines being shot.

If your brake fluid is worn out it will also cause the weak brakes.

Doesnt make sense replacing junk stock parts with other junk stock parts. You can get the Chevy cylinders from NAPA.

Have you ever flushed your brake lines?

Yeh, I have flushed the lines, all new fluid. I don't know the correct part number for the Chevy 1 ton cylinders so I had just asked for some for a 1999 Chevy. The brake line fitting was not angled like the stock part and I wasn't crazy about bending my brake line. Did the Chevy 1 ton cylinders you used have the brake line connection straight in to the cylinder or angled in from the back? Did you have to bend your brake line? If not I would surely appreciate the part number or info on vehicle you gave Napa for the part. I've already been to Napa, Auto Zone, Pep Boys and the Chevy dealer. UPDATE....Dr Evil, Thank you very much for your last post I was about to give up and just live with my junk brakes, I took out the stock cylinders that I just put in and replaced with the 1 ton Chevy and tweeked the lines a little bit, brakes are much better now. Thank you all for your help!