This is strictly food for thought and not info from me personally...just something that may or may not be true.

My brother was about to put headers on his 95 Ford Ranger 4X4 with a V6 and HIS mechanic didn't recommend them because he mentioned some bad experiences with heat coming off the headers and damaging the surrounding sensors and otherwise creating problems with a somewhat modern engine. He said they are fine for older engines without all the management devices and emission controls...but create havoc on newer motors.

I don't know about this personally. Just being a messenger.