The 20A draw is not necessarily abnormal - after cranking the alternator pumps the battery up again, at a high current initially, tapering off to a much smaller value as the battery regains the charge lost turning over the engine.

Try turning off ALL your accessories (headlights, defrost fan, A/C, radio, etc..) and remeasure the draw again. Be sure to start with a fully charged battery, this will allow you to get your readings quickly, rather than waiting for the battery to charge up again after cranking.

Fixit2003's suggestion is a good one too, try it.

With a partially discharged battery I've gotten readings of 60A initially, tapering off to a much smaller current within an hour or so. I've had the same alternator and battery ever since I bought the car (3yrs now) and it's never let me down.

Best Regards.

89 740 B230F