Difference Between 04 and 05 400exs stock rev boxes

[400excaleb]

what is the difference between them. i traded an aftermarket revbox that was on my friends 04 400ex for my stock 05 400ex one, and when i put his on mine it didnt seem to have the power that my stock one has, and his wouldnt even start up.

[trx400EXtreme]

not sure. as far as i know they are the same, but like i said, as far as i know.