How do you think he might get them back? Maybe the injection is a new and improved formula that makes him more powerful?

He was already in possession of too many powers, the writers must be chuffed to get rid of them.

Agreed. Peter got powers way too easily. At least Sylar had to actually work for his powers.

I believe it was said that they are going to combine Suresh and the companys formula, which looks like it is going to be tested on Peter.

I believe Peter got Sylar's powers for a reason. To kil his father and get his powers back. Best explanation I can think of.

how do you get more powerful than peter at his best? :S

Well he wasn't injected by Mohinder, and seemed disturbed at the idea of even getting one. It may be something to do with this eclipse. Its only a couple of episodes away and the next episode is mostly a flashback to past events. So while it was spoiled that the eclipse will take away evolved humans powers. It may have the opposite effect on Peter.

It would definatly be possible. If so, Maya would also get her ability back.

I would have to say Injection.

The only other way I can think of is he learns Sylar's hunger ability again and he kills opens Sylar up and reads his brain. And learns from that.