Engine will not rev past 4000 RPMs

[kmpdx]

Hey guys. I was on the freeway and realized that I was not getting any power. I pulled off and did a quick inspection and didn't really see anything obvious. I drove home and the car starts and begins acceleration fine but in any gear 4000 RPMs seems to be the max is gets to and then it just won't go past 4000 RPM. I plan to do more to diagnose it this weekend but anything jump out to you guys? Fuel pump? Thanks.