I checked a diagram with a 4.9 and the feedack carb system, and I believe you are correct. The EEC relay powers the computer, carb solenoid, purge canister valves, tad, tab and egr valves. The TFI ignition module is fed power separately, so the module must still fire the coil in a "locked timing" type mode, and the carb must not need the feedback solenoid to feed the engine enough fuel to run.

Thanks for that info.