383 stroker has a tough time idling sometimes

[philv]

ok every once in a while my truck wont run right. you start it, it revs to about 1800, slowly comes down to 900 where it needs to be, then drops below 600rpm's and back and forth till it dies. when its in this mood it also sputters when you woot throttle. there is no vacuum leaks, I tightned every screw on the tbi and it made it worse. now in the morning when I leave it will run just fine, it only does this every so often. but it restarts every time. suggestions???