Help us help you. By posting the year, make, model and engine near the beginning of your help request, followed by the symptoms (no start, high idle, misfire etc.) Along with any prevalent Diagnostic Trouble Codes, aka DTCs, other forum members will be able to help you get to a solution more quickly and easily!
GM dealers have a special tool referred to as AFIT (Active Fuel Injector/Injection Tester) that will run a series of tests that will verify rail pressure, check for leak down of rail pressure and then do a really "high definition" leak down of each injector where it will in percentage express how where in its contributions falls and provide the allowable spec. My similar vehicle that initially made me reply to this thread had the same DTC and using the AFIT I found one injector on that bank exceeding spec by 1-2% and replacing that singular injector corrected the issue.
