I have looked at headers also. Everything I found I think was way to expensive for too little gain. You could add an X pipe. It will deliver some of the scavenging benefits of headers and would not be that expensive. With closed exhaust the X pipe might be close to header benefits.

I don't need any more torque so I am going to go with electric cutouts that are remote controlled. I can open them any amount at any time. I don't do welding so I have been calling around to find someone that will do the job before I order them.

I had the nitrous installed at an Indy BMW performance specialist shop. I wanted experienced techs. The methanol is from snow performance and a straightforward install. I can adjust the flow to come in at any injector pulse width and be a full charge at any width as well. Nitrous cost was just under $4,000. Took 3 days to install and I had extra testing done so that took almost a week.

__________________
X5 4.6 2002 Black Sap, Black interior. 2013 X5M Melbourne Red, Bamboo interior
Dallas