03 6.0 popping and blue smoke

[jt's03250]

ok so i brought an 03 f250 6.0 with 156k miles on it a couple months ago. and i noticed a problem with it when i got the muffler and cat cut off, i would be drivin down the road and get into it a little bit and it would start poppin and blow out some light blue smoke until it clears up or i let off the pedal. it will only do it once a day when i get into it and it will clear up then it will run fine. any ideas?