1993 190e mercedes loosing power when full throddle.

Normally, if it has been a while since the car has last been serviced, I would normally start out by giving it a full tune-up. Spark plugs, cap, rotor, air and fuel filters. 9 times out of 10 this cures most issues. If you still have a problem then you can rule out everything you've just replaced. And even if it doesn't fix the problem, your car probably needed it done anyway if it hadn't been down in a while.

So on to your answer:
Loss of power on wide open throttle could be a couple things.

1. Excessive back-pressure in the exhaust.
2. Perhaps a clogged fuel and/or air filter.

One of the best diagnostic tools to purchase (if you don't already have one) is a vacuum gauge.

Here is a great description of what to look for when looking for an exhaust restriction using a vacuum gauge. http://youtu.be/d-jp1IIJVVk

Also, if you own a pressure gauge, you can make a device out of different fittings to be able to insert into the Oxygen sensor port so you can read the actual exhaust pressure. I like this method as it tells me exactly what my exhaust pressure is without guessing.

So... unscrew the Oxygen sensor before the catalytic converter/muffler, insert the adapter to the gauge, then start the car and read the pressure. View the pressure at idle, then again at 2,000RPM, if you see pressure over 2-3 PSI you have an exhaust restriction. Also the higher the RPM will show higher pressure on the gauge.

Hope this helps!
Cheers

Could be, but I would check your engine wiring harness as MB was forced by the US to use a biodegradable insulation on the wiring and with heat starts to crack and fall apart. Also check voltage regulator on the alternator and your coil.