It is a 3.1. It has never been overheated that I know of since it was mostly driven by my mom who thought going over 2k rpm was terrible for the car. The hardest it was driven was by me in college as my winter car for a year. What preventative maintenance is suggested for the overheating problem. How much money and performance can be expected with the top swap to a 3400 (also not sure what you mean here exactly). Do you have a link to the headers? I searched and could only find them for the 3800.
