22RE Weird sound

So finally got the truck together and started it up. It makes this weird high pitched popping/screeching noise. It sounds like a super bad exhaust leak but its hard for me to tell where its coming from. I torqued the exhaust manifold to spec so i dont know. Could it be the old rust inside cylinder walls from the motor sitting without the head on for too long and it's just wearing it off? Where do I start? Thx!