Hello, has anyone ever had an issue where the engine will not run up to full RPM until after rolling it to idle and wide open multiple times. When the acft is first started the engine will generally not roll up past 4400. After rolling the throttle down and back up a few times though the N2 will roll up to where it should be at 6600. Have tried everything we can think of including replacing the fuel control, governor, flow divider. Have talked to an engine shop in depth and they are also scratching their heads. Thanks for any help.