This paper presents the results from the first phase of an investigation into methods to enhance operation of integral engine compressors in gas transmission service. The project is funded by the Department of Energy's (DOE) Office of Fossil Energy and managed by the National Energy Technology Laboratory (NETL) as part of their Natural Gas Infrastructure Reliability Program, with co-funding from GMRC and PRCI. A number of technologies and methods have been evaluated and compared with baseline data, including global air fuel ratio control, knock detection for timing control, oil temperature control, high pressure fuel injection, automated combustion balancing, rod load monitoring, and new procedures for combustion balancing in automated or manual systems. Field tests have been performed on an HBA-6T and two GMW10s in active pipeline service, with a suite of instrumentation (including fuel flow, dynamic pressure from all cylinders, lateral and torsional vibration, manifold dynamic pressures, crankshaft dynamic strain, and rod load). A number of evaluations are presented, including the influence on heat rate, compressor thermal efficiency, overall system efficiency, combustion stability, crankshaft integrity, frame vibration, and torsional vibration. Some promising methods are demonstrated and some significant performance benchmarks are set.