3VZE running rich

Hello,
My name is Dan.
I recently picked up an old 90 4runner with the 3.0l 3VZE. It had a bad head gasket and made no comparison in cylinder #6. I'm aware that the exhaust crossover was to blame for this. I removed the heads and took them to the machine shop for refurbishing. They cleaned them up nicely and installed all new intake and exhaust valves. After installing the rebuilt heads and wrapping the exhaust crossover with heat tape, I also installed a new timing belt kit with a new water pump and all new pullies. It now makes good compression in all 6 cylinders at 135 lbs. each. I also replaced the fuel injectors, knock sensor, and all coolant hoses while I had it apart. It started up fine and ran well for a moment, then it started idling low and running rich with a lot of black smoke. I then replaced the air flow meter/ maf sensor, fuel preasure regulator, and reinstalled the old injectors, thinking the new ones were allowed too much fuel. However, it's still running rich. Since then, I installed a new PCV valve, cleaned the EGR valve, and installed a new throttle position sensor. None of the above seemed to help, it still idles poorly and runs very rich. Does anyone have any advice for me? I could use the help. Thank you.