Cold starting enrichment is the sum of starting enrichment and temp enrichment. The starting enrichment goes away as soon as the starter stops. At that moment the temp enrichment is whats left. It goes away fast so look quick (it should drop steadily to zero in ten to twenty seconds - a guess). It usually makes it before the O2 sensor is warm enough for the computer to start correcting.
I use a fifteen foot long harness to break out the EHA current and allow my to view it while driving the car. At any constant speed the EHA correction range should be close to any other. If the rich/lean cycle is -2 to -4ma at idle it should be close to that at any other constant load/rpm.
There are many causes tell me what you got.
Bosch Master, ASE Master, L1
33 years MB technician