I just changed my fuel pump and it was a nightmare. My 20 year old Z4 2.5i has plenty of rust underneath and everything was hard going, but long story short, disconnect the battery, remove the aluminium plate, the big steel plate including the exhaust mounts ( one wouldn't undo so I spun it out of the way), move the heat shield out of the way, remove the diagonal bar, support the exhaust, and undo the two brackets on the rear box. No3 fuel pump removal tool from Amazon will undo the locking ring on the fuel pump, but you need to modify it by squaring of the slots to make the diameter smaller, and file the ends to points to fit into the bumps on the ring, a 21mm spanner will turn is as no room for the L bar supplied to turn it. Slide the clip to pull the plug off, push the grey clip towards the filter, and pull out the fuel line. Unscrew the locking ring (less than half a tank required, or drain into a bucket) pinch the blue and yellow plug on the inside and remove pinch the clips on both fuel lines, and remove the fuel pump with combined filter. More information available and pictures of my tool mods.