The smoke problem sounds exactly like my problem which turned out to be the the oil separator.
For the brakes, I don't know why that would be connected to the smoke. If by "heavy" you mean it takes more pressure than normal to get it to slow down, it could be humidity in the brake lines. Bleeding cures most brake "feel" problems.
Has the brake fluid ever been replaced? If not, you should flush the system every year. I use ATE DOT4 racing fluid because you can get gold colored and Super Blue. They both have higher boiling points than the Porsche fluid. I replaced the original with super blue so I could tell when all of the fluid was replaced. The next time, I use the gold for the same reason. Only use new, unopened cans of fluid when replacing and throw out whatever is left. Opened cans of fluid absorb moisture so it won't be any good when you try to use it later.
The best way to do it is to get a Motive Power Bleeder (
http://www.928gt.com has it for a great price and it fits all Porsches) and bleed in this order: Rear right / rear left / front left / front right. If you have Traction Control, there's additional bleeding that needs to be done. Let me know if you have it and I will post the additional instruction for that.
Hopefully that will take care of your brake problem.
