There arent to many options here. I think you have no choice but to pull the head again. I would bet that the problem is in the head somewhere or the gasket. Obviously there is a common passage somewhere to the oil, water and combustion chamber. I realize that I am not telling you something that you dont already know. Wich I could be more help.
Your high idle condition is agrevating the situation. If you could fix that first, it might allow you to find the leak more easily. Sounds like a fuel delivery problem. Im not familar with the M102 engine so I have no specific suggestions.
Keep us informed on what you find. I wish you luck.
I got too many cars!! Insurance eats me alive. Dave
78 Corvette Stingray - 3k
82 242 Turbo Volvo - Manual - 270k
86 300e 5 speed manual - 210k
87 420sel - 240k
89 560sl - 78k
91 420sel - 205k
91 560sel - 85k
94 GMC Suburban - 90k
97 Harley Davidson Heritage Softail - 25k
00 GMC Silverado 1 ton 30k