<HTML>why don't you take a look down your exhaustpipe. There may be a small round obstruction put in by the manufactor to keep you from breaking any speedlimits.Get it out!!!
It's also possible that you have a split. This means that your exhaustpipe has a smaller sidepipe that leads to nowhere an is closed of at the end.This is also done by the manufactor for the same reasons....
If this is the case, you have to have that sidepipe sealed of (you can close the inside ,but leave the pipe where it is,so the cops don't see you've messed with it).
DON'T CLOSE OF YOUR ORIGINAL PIPE!!!!!
Both these measures will increase your speed with about 12 to 20 mph
Hope i could be of any assistance.....