I have the same chassis/motor as you and my brakes are good - after I replaced the calipers/rotors. My indications were just the opposite of yours - brakes were good cold but after driving awhile my brakes were too sensitive due to sticking calipers.
In troubleshooting I found that the brake fluid had never been changed. While changing it I noticed corrosion on both the back bleed screws. New fluid and brakes were sticking even more.
Then I noticed the brake pads were crystallized - due to being over heated at some time because of caliper sticking.
So I replaced calipers and rotors - all's well for a couple years now.
Workhorse brake issues include old brake fluid (water absorbed and expands when hot), flex (rubber) hose collapsing, brake lines run too close to exhaust pipe (add a heat sync), and the typical caliper/MC disc brake maintenance issues.
I would change brake fluid 1st while observing bleed screws for rust and old fluid for cleanliness (gook means something is disintegrating within the brake system).
Test drive and check the rotor temps (borrow an IR gun). Above 300F after a gentle stop is too hot = sticking calipers.
Go from there.
Some good info in this post that may help: http://www.irv2.com/forums/f22/02-p3...ot-173061.html
Tom and Amy from Northern Virginia.
2000 Allegro 454/Workhorse P32/TST/Crossfire
Life is a DIY project, so own less and live more