At Miller Performance, we carry STRI gauges as well as AEM UEGO wideband air fuel ratio (AFR) gauges. We have chosen the STRI brand for a number of reasons. Mainly, the ease of install, price and finish quality. STRI gauges match your interior BMW amber lighting making the install look that much cleaner. For basic AFR monitoring, we have always used AEM. The UEGO wideband kit brings you piece of mind knowing what your air fuel ratio is at all times. This helps protect your investment and allows for easier diagnostics if something goes wrong on your engine.