Steve hit the head on the nail when he said that "testing is the key".
Most of us who have occupations that require troubleshooting skills of some sort know that we go through a series of testing approaches (in IT, it's called "debugging").
While I can't apologize for all of us for some of the relatively poor advice that we may have dispensed, I am sorry that the OVP did not solve your problem. The serial numbers I quoted were drawn from a previous thread I had read. Given that you are struggling with a problem that was similar in nature to what I had experienced with the same engine and model, I sought to give you a bit of insight from my experience that solved my problem.
The OVP took care of that in a heartbeat, and from the threads I've read, many others gained from swapping it out.
Of course, many of us cured our own nagging headaches simply by taking aspirin, while others may have headaches that are caused by some other events that aspirin may not solve.
Consider that while there are a few of us that are bonafide MB experts, the rest of us Joe's are simply MB owners that are looking for alternatives to running to the dealership everytime our cars hiccup! And if someone can recall a similar experience to our own with a solution that worked, then we should probably take it with a grain of salt. Alternatively, my lack of knowledge of MBs in general would never have led me to the OVP, no matter how much diagnostic skill I possessed.
Again, I apologize for the expense you have incurred from the "parts-throwing" advise I dispensed. I hope you find the solution to your "hot-start" problem soon...with proper diagnosis.
I hereby from this day forward, refrain from shooting OVPs at threads entitled "W124 hot-start problems"!!
2009 ML350 (84K) - Family vehicle
2001 CLK430 Cabriolet (71K) - Wife's car
2005 BMW 645CI (124K) - My daily driver
2012 Mustang V6 (60K) - Daughter's car