I've struggled with similar gremlins in the past, and have thus far not kept up with the consecutive problems. Since you just did the vacuum lines, it's most likely that the problem lies there. I know how much you don't want to tear into that rats nest again, but there is probably a misrouted, leaky, or pinched line somewhere. If nothing raises any red flags there, check for leaks in the intake and while youre at it, you might want to clean the MAF with the special MAF cleaner, don't use anything else. With a 1504 its nearly always a vacuum leak, I'm sure you tested the pressure because you recommended that to me a few weeks ago, but man this vacuum system is a headache. I feel for ya, because my miller is still not happy with me, but one day, when the engine is happy, we will be too.