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Milky white water from the exhaust sounds like it could be a pinhole in the transmission cooler. I'd check your transmission fluid to see if it looks like a milkshake. Even if it looks ok, I think I'd still have the cooler pressure tested.
Sorry, I'm not much help on your EFI issues. As far as I'm concerned, progress stopped with the Holley 4160 and electronic distributors. If anything, I would check the wiring to the engine coolant temp sensor and the sensor itself. If the computer always thinks the motor is cold, it will run the engine rich for warmup all the time causing a gas slick and poor fuel consumption. NOTE: The EFI should have its own Engine Coolant temp sensor separate from the one that controls the gauge on the dash.
Last edited by DKJBama92Mariah; 06-24-2015 at 06:01 PM.
1992 Supra Mariah - Red
PCM 351HO 285hp - PCM 1.23:1 Transmission
OJ XMP 4 Blade CNC 13x15.5RH
"People do weird things to boats" -Unknown