One of the factors in fuel delivery calibration that is sometimes overlooked is that of fuel pressure. A key point to remember is that the ECU (ECM) does not monitor fuel pressure. It always calculates the fuel injector duration assuming the vehicle’s set fuel pressure. If there is a restriction or other problem that changes the fuel pressure, the ECU (ECM) will not compensate for that and the resulting fuel delivery will not be correct for the operating conditions. When diagnosing a drive-ability or running quality issue it is important to verify correct and proper fuel pressure. This includes the fuel filter, an often overlooked item in the diagnosis of running quality problems. You should know where the fuel filter is on your sled, how often it should be replaced, and when the last time was that it was replaced. Never been replaced? And you have how many miles on the sled?