For corrected, updated information, skip ahead to: http://www.advrider.com/forums/showthread.php?p=26886395#post26886395 As part of my Wideband O2 project I dug into coding plugs and thought I'd share what I found. For R1100 and R1150 Motorcycles, BMW devised a Coding Plug and socket located in the Fuse/Relay box as a method to control different engine configurations (intake tubes, valve cams, cylinder heads) and to manage the engine with and without a Catalytic Converter--exception see 1993 R1100RS note below. While trying to figure out if there is a richer map in the 1150 (a hidden, surge-free, higher performance map) I got frustrated by the lack of a specific description by BMW of what each setting of the plug is for. Eventually I found a French BMW document (circa 2006) and BMW Bulletin 2701 dated 9/22/95 (and 10/31/2001). I also researched each configuration of 1100 & 1150 in the MAX BMW online parts database. For the 1100 series, BMW 2701 indicates that there are 6 engine/exhaust configurations that can be coded. I can not find any documentation on the number of maps in the R1150 but in the US but from the parts lists, I see 3 different plugs that are used (all for bikes with catalytic converters). The configurations are designed to control fueling maps and spark timing maps. The fueling differences are small except for two plugs on the R1100 which allow Open Loop operation. On the R1100 those maps are about 5% richer at low throttle angles if you use gasoline without ethanol, with 10% ethanol the maps are not much richer at small throttle angles and are leaner in cruise compared to closed loop. A simple way to divide the 6 R1100 maps: 4 are for cat equiped motorcycles, and 2 are for non cat equipped. Or a different grouping of the configurations: one is for shorter, larger diameter intake tubes (and cams & heads), one is for longer, thinner intake tubes (and the cams & heads), and one is for lower power or lower octane fuel. The coding plugs have four pins (numbered 30, 86, 87, 87a), pin 30 is a Motronic ground. Here is what the other 3 pins seem to signal: Pin 87 Grounded: Tells the Motronic that a catalytic converter is installed. Those maps are designed to arrive at an Air Fuel Ratio of 14.7:1 in the cruising range. Pin 87 Ungrounded: On the R1100 if this pin is NOT grounded, the Motronic would look for a CO potentiometer. Since the CO specification is 1.0 to 2.0%, which implies an AFR between 13.8 and 14.1, and this fueling map is designed to arrive at an AFR of 14.0:1 with the co pot adjusted and at small throttle angles.. On the R1150 ungrounding pins 87 and 87a on my R1150RT produced a somewhat leaner AFR than with both grounded but the bike still operates in closed loop. Pin 86: On the R1100, if this pin is grounded, it tells the Motronic that lower octane fuel, lower power is expected, and/or the motorcycle was shipped to Switzerland. In the US on the R1150GS, this pin is grounded for models allowing lower octane fuel. I don't know what's special about Switzerland but I'm guessing that Pin 86 is a signal to retard timing compared to other maps. Pin 87a: This pin is grounded or not, depending on which type of intake tube, valve cam and cylinder head is installed. Pin 87a R1100 models: Grounded for intake tubes 137 1134 1405/1406 (longer and narrower); cams 1560--on the R1100R and R1100GS. It is ungrounded for models R1100S, R1100RS, R1100RT which use the shorter, larger diameter tubes. Pin 87a R1150 models: Ungrounded for intakes tubes 1405/1406, etc.--R1150R, R1150GS and R1150GSA. It is grounded for models R1150RS, R1150RT (with the shorter fatter intake tubes). Pin 87a Fueling Effect: My guess is that the longer narrower tubes have a lower Volumetric Efficiency and need less fuel at some points in the fueling map. Therefore if you signal that fat tubes are installed (ungrounded 87a on the 1100s or grounded on the 1150s), and then install the long narrow tubes, you will get a richer mixture in parts of the fueling map but the process of closed loop mixture adaptation mostly negates this. Summary The Techlusion Manual probably sums it up best: before installing their product, they advise that you install the correct Coding Plug for your BMW model and then reset the Motronic. If you have a catalytic converter and a stock O2 sensor the bike will eventually operate closed loop at an AFR of 14.7:1. And then its adaptation functions reverse any gains that a different plug has temporarily brought. I know that others have had different experiences and some will disagree but it seems to me that the Coding Plugs are not the best way to try and richen the mixture of R1100s and R1150s, with the exception of No Plug on R1100 models running non-ethanol gasoline. RB N.B. The 1993 R1100RS had its coding hard-wired (no plug socket) in the harness when shipped with a catalytic converter; but if it was shipped with no catalytic converter, it had an empty plug socket so a converter could be added later.