Help!! Ok...I'm having the same problem before and after the SP1 install. Take off out of SEA, FMC loaded with ZFW of about 121.0...Used TOGA...Gear up, Flaps up...showing normal Climb N1 with Autothrottles engaged. Empty Center Tank fuel to keep the weight down.....but the plane is acting like it's barely single-engine...barely making Flaps Uop speed in level flight.Any ideas???Thank you so much!!!Ed