Yes, I have replaced the connectors. With the intake backfire that happens, does this point to a lean fuel condition? Other than the fuel pressure regulator, I have not gotten into the fuel system; I did check the purge valve and clean it. I have checked for vacuum leaks as well. The car seems to run well until operating temps achieve closed loop operation and then all of the symptoms start. We drive the car every day and I really would like to get everything ironed out. I am thinking about buying 1 fuel injector for diagnosing them one at a time. I feel like I am running out of options.
Thanks,

Bill

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87 560 SL
93 300E 2.8
91 300CE-24