Hi Benny, without going into too much detail, what is the difference in sound between the two? Is it necessary to change the back boxes or won't I see much difference if I leave everything else as standard?
If you keep the standard rear boxes then the difference is is more subtle from standard.
Its noticeable but not too much in your face.
I will post a couple of you tube links. Showing a 4200 with a H pipe and standard rear boxes and then another video of the same car with a H pipe and tubi rear boxes.
Sparts / contigo also has a video of a H pipe and X pipe comparison video on another car.
Listen to them with headphones on and they should give you a much better idea.
There is a metric **** load of sound deadening material in the standard rear boxes.
You can probably have the rear boxes modded at a later point if you wanted more volume by either just removing some or all of the matting and have the option of retro fitting valves to give you quiet and loud mode under 3000 rpm.
X pipe is a higher pitched scream and the H pipe is a lower pitched growl.
You have to excuse the contigo / sparts video as they clearly had a bmw/audi indicator system fitted to the car. Indicating left while turning right !