Did a convertion to a Toyota 4 runner.

I have it in and running but it seems to be a dog? Ik lack of power. And I can't hit 50 MPH easily.
I have replaced the 2 fuel filters.
I also have some valve adjusting tools on order.
I did check the valves and they are all tight. Is this most likely the casue?
Sorry for the dumb to you questions but I am very new to diesel.

As soon as I read my Mercedes shop manual and understand it better I will check the IP and timming.