Most of the timing difference is thru the "MAP" that is designed into the EZL(ignition module). However removing the resistor will add 1-1.5HP at the rear wheels.
If you do go with a replacement cam remember that unless you do something with the exhaust system then it won't help much at all.
The EURO versions all had catalytic converters starting when the W124 chassis 300E was released in 1985.
The fuel mixture also was richer due to "programming" differences in the CIS-E fuel computer. AT WOT (wide open throttle) there isn't any real computer control for fuel mixture.

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