strange rattle noise after engine is warm around 2500 rpm,s

truck has new exhaust from y pipe on back, that what i thought and replaced everything, rattle still there

Best way to locate rattle is put it up on 'driive-on' lift that has the front and rear suspension jacks... Run vehicle and try to duplicate noise... Drive on lift with jacks will keep truck oriented as if still on ground which will improve chances of finding noise... May just need experienced mechanic to test drive.. Good luck.