Can a federal Complaint in a pro se civil lawsuit state conclusions based on the evidence, or only evidence?

I'm filing a civil lawsuit pro se. The Defendant's attorney said some allegations based on conclusions were misplead. Can I make conclusions based on the evidence, such as, "Person X provided Plaintiff with a fabricated wheel bearing part that didn't belong to Plaintiff's car after it was serviced for repairs. Therefore, person X fraudulently concealed facts about Plaintiff's car"? Please respond.