[92 Golf 1.8 gas]

I just hit a puddle in the pouring rain last night and yup, the engine let go on me. I'm pulling my hair over this. Here goes:
I've changed my:
-Ignition coil
-Full tune up(wires, cap, rotor, spark plugs, air filter last year)
-Control unit
-Cooling temp sensor
The battery is new and the terminals are clean.I even went as far as changing the alternator, but that was another problem in itself.
Now i'm shooting out black smoke everytime i start the car and doesn't idle right ever since last night. I have spoken with more then 2 mechanics who tell me it's either my Mass Air Flow, or my Oxygen Sensor, or my timing belt skipped a notch.
This has been persistent and i'm spending lots of dough at the same time for nothing thinking the problem is solved. I love my golf and i don't want it to end with something like a compression problem. Can someone please guide me in the right direction to go about solving this problem.
Thanx a mil.