Just a little confused, If your checking amperage across the positive and negative side of the battery, that wont work. Amperage needs to be checked in series and not in parallel. A 2.8 amperage draw is equivalent to the draw of a head light. That's a heavy draw. Moisture and dirt across the posts of battery can cause a draw. You can also have a bad ground, current feeding back from ground. It sounds like your checking all the right things, just need to keep looking. Not sure if your car has an insulated positive junction, on your radiator support by the battery, but if so I would check that. Like Dave said could be wiring harness, check for obvious damage. Also pull apart your bulk head electrical connector at the firewall. Look for moisture, dirt, bad connectors. Blow out the connector, clean the contacts and put dielectric grease on the contacts. Good luck, keep up informed.