Hey guys I am getting a misfire on cylinder 1 on my 06 expo with 160k miles. The local Ford service manager and I went for a drive with his computer hooked up to find that it was cylinder 1 because it was not throwing a code. It only does it around 3,000RPMS and up. We tried swapping coils and it stayed on cylinder 1. We swapped cylinder 1 plug thinking maybe it was overtightened and porcelain cracked but that didn’t fix it. He also did a test on the injectors and they all read the same. Now he said to pull the valve cover and check the springs. Anything else you guys can think of before diving in to that? Thanks in advance.