vortech header + exhaust + no cat
 

is the car supposed to be faster if you install a j's N1, mugen header, spoon test pipe on a vortech supercharger?
The car already has an invidia dual exhaust and vortech supercharger.
Is is worth changing it to the above?

The Mugen header is supposedly not a good choice for an SC. You would probably get better results from a Toda header. I haven't heard much about the J's N1 exhaust, but if it is 2.5", you would probably do better with a 3". Test pipes are all the same, and do help.