SEI lower units

I installed an SEI lower unit and went thru break in process as recomended. I was out running around and noticed an inability to get to my rpm of 5400 and my speed of 53 mph. I was only running about 4600 and around 43or 44 mph, if my memory serves me correctly. I believe the change is due to a different gear ratio in the new lower unit since nothing else has changed. Has anyone else had this happen? I have e-mailed SEI and they have not replied.
1999 Evinrude 175 FICHT, Mod# E175FPLEEC Ser# G04615125
Thanks, Pete

The gear ratios are all the same even if you look at the lightning lu. the only difference is the shape. Got to be an issue somewhere else.

just replaced mine with a sei broke it in and turning same rpms with it 225 jonny