Does Big gun race slip on loose top end speed.

[yellow400]

Does the big gun race slip on loose top end speed for a 400ex. I was just wondering if anyone has this slip on and what they noticed. If you change the size of the main jet up, will you notice more gains with the pipe? And i heard that it was a bottom end pipe, so does that mean that you loose top end. ANd what is a better pipe FMF titanium 4 slip on, or big gun race slip on?
thanks