I never felt any misfire until a few weeks ago, which led to further inspection and finding out my injector at #1 was done for. When the injector was pulled out, the lower o-ring stayed in the rail, so I'm thinking it was once changed and the wrong o-ring was installed. I have some "tune-up" items in the mail from IPP, so I'll be doing everything at once, which will hopefully make the Z purrrrr like a kitten again.