Dave:
Yes, I think everyone on this forum has probably contributed to this topic to some degree at one point or another. What KTBD said is correct, however you need to understand the following as well:
You have a dry sump motor that uses a very reliable high-pressure variator and VVT system used in the Ferrari F430 and Maserati Camboicorsa/Grand Sports. It is of the helical spline design that rotates forward with pressure, similar to the Alfa Romeos, which ironically suffer from a similar problem. The dry sump engines do not need re-machining as the check valves and caps are already equipped and are proven to work as is in every application other than the QP. The wet sump units are completely different in design and require the update.
It is very interesting that you mention the accumulator.
What intrigued me about this whole issue is that the wet sump units typically fail one side at a time, at least the one's I have witnessed. I sure there are exceptions. However the dry sump units typically fail bilaterally - in other words, both banks fail at the same time - otherwise they never, ever fail. Odd. Additionally, I know of well-serviced, low mileage, spotless cars with serious variator failure and other neglected, filthy cars that are silent on startup for life. It is not dependent upon oil changes, etc. Living in South Florida, where QPs grow on trees, you see a very large cross-section of examples that allow people like me to make such statements.
Anyway, back to the accumulator. The fact that the dry sump units fail bi-laterally or not at all leads me to believe there is something behind their operation causing this. Could it be the driver? Searching for common denominators of failed cars vs. those equipped with the same setup (like a QP vs a F430 or CC), the QP is the only car that defaults to Auto when started. So, I began to think that maybe it is a result of a very heavy car spending most of its useful life in the low RPM range, lugging itself and starving the VVT system of oil, thus accelerating its wear. Could be. Then, I thought "why would both sides fail?" Is there something in the mechanical process that could cause or influence failure of both sides simultaneously? That's when I looked at the accumulator.
A good friend of mine just completed the Maserati academy and is employed at a Ferrari/Maserati dealership. He shared with me all his training collateral, photos, etc. on variator service. HERE'S WHAT SHOCKED ME. They no longer train on dry sump engines, although the training manual reads "parts between the dry and wet sump motors are different by 80%." They simply state that the replacement process is the same. There is no training on the function of the accumulators. Those who were willing to share what they know, all described the part performing different functions and even the legacy techs said to me "the only thing we've ever done was replaced them when they leaked externally, which is rare." I asked what it does and my response was "we don't know, really." Some say it supplies oil pressure on startup; others say it is only during the advance/retard at 3000 rpm.
The moral to the story is this - I am replacing mine to be safe, just prior to replacing my variators. I am not replacing the variators myself, but I have replaced my variator solenoids (very easy job), and will be replacing my accumulator and pump just to be safe. Then my variators will be replaced. If you search my previous posts, my car has had a viscious rattle almost since the car had very LOW mileage - it is not at 102K.
Anyway, whatever you can find out would be appreciated. It would be interesting to see if changing out other less expensive parts early in the game changes anything. Like if your accumulator was changed out - would that solve anything? It's only a couple hundred dollars. Maybe worth a try.
As far as your specific questions about what actually fails, maybe Jason can chime in. He does these repairs like clockwork and could probably give the most trustworthy answers.
