Antifreeze cloud coming from my Chevy Tracker's exhaust. Help?

My '03 Chevy Tracker 2.0L-4cyl intermittently leaves a white cloud of antifreeze smelling vapor out the exhaust. There is no water in the oil. There are no bubbles in the radiator. No external signs of antifreeze. When it cools, it sucks about all the water from the reservoir.

I had the head milled, pressure tested and re-installed with new head gasket & bolts. The coolant lines run into the intake manifold, head and block. The mechanic said he did what he could to test the intake manifold. (whatever that was.)

It ran a while, but a couple days later, did it again. He checked it a while, and we considered the possibility of a block leak, and put in some "Stop Leak", which he simply added, rather than draining, applying, flushing.. ETC.

I drove it for about 2 more weeks and it was OK. Then, I'd shut it off for a few minutes. When I restarted, it kind of missed (nearly caught but didn't). So I restarted it and immediately a 6' cloud of antifreeze. But the drive 3/4mi home didn't have a cloud.. but I could see signs of it.

Help! What to do. I really love this vehicle and they stopped making them. Is there a fix for this or should I consider a complete engine package from a junk yard??

Thanks a bunch.. 10pts for the best answer....