blueish smoke from new rebuild...gutted cat though?!

hey guys i just recently started and drove my 8 after a complete engine rebuild. so when i first started driving her, it would stall at every light. did the brake pump 20 times in 8 second and since then it has'nt stalled and the car starts right up! ok cool, everything is fine....now i gutted the cat prior to the motor being installed (chunks of cat pieces were rattling inside) so now the car runs good and then at a stop light/sign the car lets out the blueish smoke. again the cat is gutted and the motor literally has 13 miles on it off the fresh rebuild. i changed plugs and wires (coils are next) giving me 3 cel codes, misfire cylinder 2 and fuel lean mixture and one for the cat obviously....any info on why its smoking would be cool....