FYI, doing the above does not put a load on the engine, it must be driven and driven somewhat hard to seat the rings. Simply revving it in your driveway did nothing.
Breaking in a motor usually consists of just breaking in the rings. It's not that you haven't broken it in properly, it may "possibly" be the rigns havn'et broken in yet, (If the cylinders became glazed over to soon from synthetics, heavy loads with conventional oil should still help the rings seat) but with the mileage you've put on it I find that unlikely. (Feel free to disagree, I could be wrong). The way I like to break my motor in is by going out on the interstate get going about 30 MPH. Then gun it through all the gears. Let the motor rev itself back down to around 30 MPH. (down shifing occassionally.) Drive another mile or so to let the rings and piston cool down. Do this again, and repeadily until the rings seat. Change your oil and your motor is broken in, IMHO.
There are a million ways to break in an engine and everyone has there own process. This is just MY preferred method because it gives the rings a few seconds to cool in between heavy loads.
Did this just start happenning recently or has it been doing this the last 20K miles?
keep in mind a newly built motor will smoke badly when first fired up ect...from all the new parts breaking in ...usually smells "funky" also...mine did this but after a period of time the smoke and smell went away...make sure its oil smoke your seeing