A new shock
 

I've been thinking, is it ok for my Fuel's frame if I can swap out my air shock was lets say a Fox vanilla with that oil thing attached to it (or whatever it is.) If that can work out, will adding a 650lb++ spring affect the frame? I dont want it to break or something like my bruiser lol.

I think it would be fine, just make sure to get the correct eye to eye length.

Oh and that oil thing attached to it is called a piggyback reservoir or just a reservoir .

Make sure the eye to eye is right. And it is has an external resevoir double check with Trek that it will fit.

Where could I get a spring with a high lb rate? On the bruiser I could sag it 90% just sitting down, and i was 240ish on 650lb one.

the "oil thing" is called a reservoir, research is a good thing :-)

So is bikeforums.