Header with DASC
 

I've read over and over again that the stock BMW M44 header is so good that it's not worth investing in a performance header. This may be true on a naturally aspirated car, what about a car running the DASC? I'm almost certain that a header such as the Supersprint (or Ebay clones) would free up some horsepower, but I can't find any data to support this.

My Z3 has a DASC with the 3.6" pulley and the Technique Tuning stage III kit, so I'm getting about 9-9.5 psi. The only other engine mod is a Supersprint cat-back. The supercharger forces far more air than stock into the motor, so I think that opening up the exhaust can only help, right? I'm interested in trying a header (and cat delete), but before I do so II really want to hear from someone who's done it or has seen dyno graphs, etc. Any input would be very much appreciated.

Leave the header. The restrictions start where it connects to the collector then to one pipe that I think is 2 1/4". I went 3" from the collector back and it flows...