front end steering play

here is one fior everyone out there. I have a '98 Chevy/GMC Sierra SLT with 93k on it. At about 50k i replaced the idler and pitman arms, steering was great and tight till about two weeks later(common with these trucks) when it got loose again. I have had it lined up by different shops, checked the front end by a Chevy dealer, GMC dealer and myself(i am a mechanic)i just wanted to confirm my findings(everyone states the front end is fine and tight). The problem is the front steering is pretty much dead from 10o'clock to 2'oclock and then it kicks in. i even changed the steering box to an AGR box(night and day for response)but the dead play still there. the steering sensor seems ok, i don't have the same problem other do with the sensor unless mine is having a different problem and this is another symtom of the bad steering sensor. Please advise on what this could be. It is almost unsafe to drive. :banghead: