Jetta III, white smoke, NEW headgasket

[BDizzle7]

I bought a 97 Jetta III GLS several months ago, and a while after I bought it, it had stumbling idle, would stall at idle every once in a while, especially if I tapped the gas and let of quickly. Then i noticed there was white smoke coming out of the exhaust. It would smoke only a small amount when first started at idle, when warmed up it would smoke a little bit more at idle, then if you hit the gas it would smoke quite a bit. After some thinking I came to the conclusion that the most likely problem was a bad headgasket. Rather than spend large amounts of money to have a shop do it, I bought the gasket and did it myself. After this it was worse than before so I gave up for a while, but eventually figured out that the hall effect sensor happened to go out while I was replacing the headgasket. I finally got the part and fixed that and it runs much better now, but still smokes just like it did before. With the headgasket out of the way, I would guess this leaves a cracked block, cracked head, or a blown seal somewhere. Are these the only 3 possibilites? If so, do you think 1 or 2 treatments of block sealer will fix it (thats what im planning on trying next)? It runs fairly smooth except the idle slowly fluctuates back and forth sometimes, and sometimes will stall, but seems to run a bit better than before I did all the work to it. Thanks in advance for any help, I would really like to get this figured out.

Edit: It has a little over 100k miles on the motor