atm i have a set of 4-2-1 extractors and have got a crack in, wos wondering what the diference in power is between these and 4-1 styles?

Ive looked into this many times,
most people are of the opinion that 4-2-1 is better, but depending on the engine a well designed 4-1 style will offer a similar result
I personally believe that the 4-2-1 is better as it encourages a transition into the single pipes

http://www.zerotohundred.com/newforums/features/390895-4-2-1-4-1-extractors-broken-down.html
this article on another forum shows a graph, unsure the accuracy of it thou

Its said in several places that with a decent tune or re-map, a 4-1 header should make more top end than a 4-2-1 header.
But they also say that a 4-2-1 will make more midrange


so it all depends on what the end result is that your going for

true thanks for the help, with what it says i think the 4-2-1 is good for what i do general street driving :P, till i get the head work done