Ok so I have a 2001 f350 5.4 that recently developed a skipping problem. The truck starts fine and idles fine. But it will randomly start skipping bad and stall unless you floor it while it's skipping. Flooring it will clear it up. I thought it could be the iac valve so I replaced that but it still skips. I also noticed their was oil in the throttle body and replaced the PVC valve. That didn't help either. At this same time I put a new air filter in it. And last year I did plugs and coils. It also does not throw any codes when this happens. Any ideas?