The torque band of a stock 454 MPI is 4600-5000 RPM at WOT. So at 4200 RPM you are lugging your motor. However with a 22P Lab Finished propeller you should be there. So you need to verify a couple of things.

Confirm Your:

Propeller pitch
WOT RPM, verify your tach.

Additionally I would verify your speeds, via gps and verify your gear ratio.

When testing for WOT RPM you should also be trimmed for speed when recording this data.

Julie

I thought the 310 and the 330hp motors were carbed that ran 4200-4600 and the MPI motors were 365 and 385hp and ran 4600-5000. There was a 310hp MPI motor?

noboat is right. It is sometimes difficult to remember all the 454 combinations built. The 454 mag mpi is 385 hp fuel injected and the WOT range is 4600-5000 (not the torque band), with a rev limiter @ 5150(if stock). The torque actually falls off slightly after 4600. I would agree, Labbing the 22 Bravo 1 is a good idea. Another great prop is the Rev 4 Labbed at 21P.