Hey buddy. So, adding the headers and keeping the rest of the exhaust stock is a safe move. But the rear muffs kill quite a bit of performance and economy and sound. The problem I ran into in cutting out the rear mufflers was the resonators I put in place. To small. It is an Aero AR25, which are used for the S54 powered BMWs to cut rasp, etc. I tried it as a stand alone. My X5 sounds wicked, just about a 2000 rpm drone that bugs after a while. I know from my previous e53 that the magnaflow 4 inch rounds (14 or so inch body length?) sounded awesome and I don't remember any drone, or if so it was very small.

Anyways, I decided that I want to experiment with a few different setups, and then build a 304 stainless system from the headers back. I'm working out tube size and different options on the middle resonator. I've got a super awesome option for the rear mufflers. We have been limited on what we can put back there due to size and angle constraints, etc. More on that later.

X pipe is getting cut out as we speak and two glass packs added to further experiment. I'm getting new hardware for the middle resonator connection, so I can scope the internals. My current hardware is rusted and won't come out without breaking.

The x pipe I chose was not the best design. It was stamped and had quite a bit of internal space. It acted more like a hollowed out echo chamber. You don't need that much space. Honestly two pipes with a ever so slight shared wall or merge is all you need. They don't have to cross over like an X. Ideally just enough to help scavenge the pressure waves/low pressure tail of both banks and increase your volumetric efficiency. The X pipe I put in was rubbish. I'm leaning toward a borla pro Xs dual in dual out with a built in resonated X pipe as a trial.

Hang tight over the next 30 days. Once I have finalized my design, I plan on making a few extra header back sets to sell. Gotta practice my tig welds! 😄 PM me for details.

__________________
2005 X5 3.0, 6MT, Alpine White on Truffle Brown, Sport, Preim, and Cold Weather, Alpina Stainless Headers, AFe Intake, UUC SSK, OEM 87's, 3.64 Differential Swap,Performance Modified Euro 2 Tune, UUC LTW Flywheel and HD clutch, Bilstein B12 Suspension kit
Future mods ZHP/Schrick Cam Shaft upgrade, Operation code name:Doppelschrauben-Kompressor

Wife's Ride: 2011 e70 X5 351 M///Sport.

Also in the fold: 2004 X3 3.0, 6MT, Black Sapphire on Terracotta, port, Premium, Cold Weather.