Unless you still have the ESA, try experimenting with your timing if you're looking for fuel economy. Namely, experiment with more spark advance. In light, part-throttle driving engines like timing--a lot of it.
Optimizing timing should be done by virtually everyone with a distributor that has some kind of advance mechanism. Why? Base timing on every production car ever built is, by necessity, a compromise. The base timing on a manual-transmission base '76 Volare coupe is the same as in a full-boat '76 Coronet wagon, regardless of engine (as long as they both have the same engine, that is). They didn't alter it across models or options, so the engineers had to designate a timing setting that would work in a worst-case scenario; if Grandma just drove the F-body to church by herself in Seattle it's a lot less load than if Uncle Elron put on a class 3 hitch and decided to tug a 28' camper and all five kids up Pike's Peak.
There are a number of ways to skin this proverbial cat, but I think the most-enjoyable and easiest method is the "Big Fat Friend" procedure. If you've got an aftermarket camshaft, carb, exhaust, etc. you might be surprised how much timing you can actually put into the car, which will not only increase economy but overall performance. In my stock 340 I ran 12° BTDC without problem; my mildly-built 440 was at 15° and my Pontiac 400, slow-burning bastard that it was, was set at an astounding 24° BTDC (it was also nearly impossible to start while warm on an average summer's day). I can't remember exactly where it laneded on all my cars, but rarely has my base timing ever been below double digits. Not surprisingly, my 400 Poncho got the best economy of the bunch. Incidentally, the guy who bought that car from me backed the timing off to 18° BTDC base. It slowed the car down a whole bunch, but damn if it wouldn't start every single time. :icon_biggrin:
