My 03 300 has developed a ticking noise at idle,as you throttle up it goes away,then chop the throttle afew times it revs down and dies.I have read of the rattling noise due to pv out of adjustment.This is not a rattle but a ticking noise,sounds like an exhaust leak,but doesnt seem to have one.Any ideas? Thanks.Bty,it has weak power at low rpms,then hits hard mid and top.