I have a 1988 190E 2.0-liter in Europe and was wondering if anyone knows of any cheap and easy ways to increase it's engine performance.

Have you tried the benzsport.com forums? Most of the folks over there have older benzes, and they're always talking about tweaking this or that. Give it a shot, they're a good bunch of people.

There is a resistor in the ign wiring harness that determines how much ign advance the car runs. Changing its ohm value will allow more advance and better performance.

Check out www.mercedesshop.com for a long thread on how to do it.