what are you rnew driver disntances and current 5i distance? what kind of slice is it, a pull slice, a strait then slice, a push slice?
just a guess.... maybe becuae of you short game you have switched to a bit steeper swing and maybe you are hitting the ball on the downswing off the tee giving it high backspin thus killing distance

as far as your 3w sliceing but not driver.... sounds like a bit of a mental issue maybe, it is harder to do with thoose certain clubs, but when people have problems with clubs i would say have friend hand you the club and don't look at what it is and just hit it normal..... but it is kindof easy to tell the difference between a 3i and a 3w and a driver.