M5 Guru (>2000 posts)
Join Date: Nov 2008
Location: New England
Thanked 754 Times in 613 Posts
Before throwing a bunch into it, shotgunning in troubleshooter's lingo, you need to just drive it normally for a bit. Run the tank down to about 1/4 or 1/8, refill the tank and drive it some more. Throughout these two or so tanks, do a few pulls and monitor operation. If the problem persists, then we can talk more.
2/2001 M5, Jet Black, Exclusive Complete Black Walk Nappa Point Heritage Leather, Black Cubic Trim
8/2011 X5 xDrive35d Sport, Black Sapphire Metallic, Black Nevada Leather, Fine Burr Walnut Trim