So much fun to work on that I should be very happy. Happy because I have more work to do. Bad news, good news. The ECU swap did not cure the high idle, although somehow the throttle response feels crisper. Maybe real, maybe imagined but it feels real. It wouldn't surprise me that you could feel minor differences between ECUs when they're this old.

The good news is that I found the definitive vacuum leak. I was still suspecting the intake manifold and that's what it is. Number 3 cylinder particularly and I guess I was too dainty with my spraying and it was evaporating before it had any effect on the leak. Seems to be on the underside of the manifold which made it a little harder to track down.

Thank's Art for suggesting the Bentley F.I. book. I'm going to look for it and place an order.

Post note: Funny thing is while I've been working on this problem the high idle is not as high as it was. Down to about 1100, almost acceptable but not with a manual trans. Since this car sat SO much and I did snug up the manifold bolts, repaired a couple of obvious vacuum leaks and cleaned and reset several components, it has been steadily improving. It's a great driving car now.