[Bob Kontak]

Cool. I had a similar experience with my SC.

The O2 system on my 81 has a relay next to the CIS brain under the passenger seat. It is square not round like the ones in the front trunk. A guy was saying his car ran better just by replacing this relay even though it was not bad. I did it for fun and it really made a difference. Crisper feeling. Not faster - just better response. Like a tune up.

I was thinking that maybe your temps dropped so much that the colder air made the car run better - but it's 70 degrees in Bel Air after 10PM.