Yip, just another non critical monitoring device on the car. (SARCASM!)
Car and Driver Magazine needs to write more than reviews and print oil and air filter ads in their mags. Apparently that is what many S550 owners reach for rather than a real muscle car magazine or a performance how-to series on engine theory and tuning management or something that would actually educate a person on something more than a skid pad statistic. 
In my case is stands for Power Pack 2. Search for M-9603-M8A.Probably a stupid question, but what does PP mean? I've seen this acronym used all over the forums and, try as I may, I can't seem to infer its meaning from the context.
My vacuum gage is pinned to 25 in/Hg when at idle, is that way to low?Yip, just another non critical monitoring device on the car. (SARCASM!)
Develop a crack in your plastic intake manifold and see how important vacuum monitoring is. We know that this never happens though right? (More sarcasm)
A car with stock cams (even a boosted car on a stock engine) and stock top end should idle at 15 inches of Hg (that's mercury) minimum. Most Coyotes and 4.6L 3 valves will idle between 17 and 20 inches. As idle increases so does the pressure in the engine vacuum decreases with the introduction of atmospheric pressure...IOW the throttle body blade begins to open at throttle command). Begin adding cams (or run a stupid ghost cam idle) and your vacuum is going to read closer to static depending on how much overlap the tuner has generated via VCT to create the cam sound effect. My 2005 idled at 12" Hg after warm up when the cams were added. It idled at 7-9" Hg on cold start.
One of the very first things to look at when idle becomes rough or there is a miss at light throttle is vacuum. But its really not that critical right?
Yeah! Any of you figure out a way to make the vacuum gauge into a boost gauge?
In my car the vac gauge becomes a boost gauge when I press my right foot down on the small peddle.Turn it upside down
Mine hits up to 15.1 at idle for a split second at times. I’m still chasing issues with my new car, Ford and my tuner haven’t had any answers it sucks
Drill down one more level and you get a faux analog gauge which displays meaningful information.
No tune is ever going to be perfect, especially an aftermarket one with fuel modifications. Hitting 15.1 for a split second then going back down is perfectly normal, it will always fluctuate and rarely if ever be constant. That's what the o2 sensors are for.
Yeah, that's one of the things that bugs me. They have enough data to position the digital needle on the digital gauge, so all they need is a little software to come up with numbers instead of Normal or Cold.