Battery drain when everything off

I have a 1995 Suburu SVX which shows a current of ~1 A with the engine
switched off and nothing else on. I tested this by putting an ammeter
right at the battery in series with the ground lead. I realize the
computer and even the radio require a small amount of standby power, but
this seems excessive.

I have tried removing all fuses, one at a time, with no change in the
current. I've looked at all the usual suspects like glove box and trunk
light. This occurred after the replacement of a knock sensor, which was
causing the "Check Engine" light to stay on, but may not be related. A
previous similar fault was caused by a bad electric door lock circuit,
but disconnecting that does not help. It passed the California smog
test OK, but the current is enough to drain the battery in a day or so.

This is my fourth Subaru, and I've had manuals for all but this one.
I'm not sure a wiring diagram would help, but I don't have even that!

Any ideas?

Virg Wall