Fuel trim numbers?
 

I have the Diablosport Predator that has some diagnostic abilities to it and I was checking out the car on the highway today. I noticed the long term fuel trims were pretty much sitting around 9.5 to 12.5 % which seems kind of high. I have the ported TB, a lid, the airbox mod and cut the EGR tube and it looks like it has helped airflow a lot. Is there a fuel trim range that means it's time for a tune like 15% or 20? I plan on putting headers on shortly so I don't want to think about a tune yet.