Checking injector wiring?

Im getting codes P0275 and P0273. I ohmed out the pins on #5 injector and they were fine. Could you guys tell me how to check the plug and harness? And the easiest way to remove the plug from the ficm? Any other advice on what to look for while Im under the hood? Ive noticed a decline in mpg and it idles noticeably worse and when in OD at a slow speed it shakes a little. 2007 BTW

sounds like an injector going out most noticeable and great to check it is to swap it with an injector with no codes. but im sure a couple of the guys on here can give you more advice