At 150K, I'd replace all of the coils, plugs, plug wires and coil connectors and you'll be good for another 150K. (Assuming you have the updated harness.) And surprise, I've found very good pricing on genuine Bosch parts on Amazon.com. For instance, $110 for the Benz coil and $55 for the same identical Bosch coil from Amazon.
Anziani
'97 CL600