So my engine harness has 3 broke connectors and can’t find all the pigtails need. My question is my trucks a 2001 but I have a 1999 engine harness as well. Can i just the connectors I need and tap them into the 2001 harness? Or what be a better way than buying a new harness lol.

You can go to a "Pick Your Part" salvage yard and cut out parts of wire harness.  This is were I get the material to make custom test leads.

You could send the entire harness to @Auto Computer Specialist they can rebuild engine harnesses.

So I can’t just cut the pieces off the 99 harness and put them on the 2001 harness ?