94 Workhorse smoking (All the sudden)

[gmtec2]

I replaced the carb this past winter because the old one was junk. I also replaced the entire governor linkage. Found the breather hose from the airbox to the crankcase missing. I opened the governor just far enough so the motor wasn't searching. I had this thing running so good and after a few days, it started to smoke. It is smoking only when there is light throttle applied, If i open it up it is fine. I just don't understand how all the sudden after doing all this work it starts to smoke. Any ideas besides the motor having to be swapped? Thanks.