Ok installed it when I did my injectors about a month ago. First primed start up I had 12.5psi got the p0089 code. Erased it and lasted bout a week before it came on. Now my pressure has raised to 15psi and I get the code every could of days. Is it normal for the pressure to raise by itself? And what should the pressure be at? With code active, truck run perfectly normal, I just have the mil light on. I've been searching and can't find anything about the pressure rising by itself.