the car is Mechanical Fuel Injection
Fuel is metered by air flow through a meter, which has the benefit that if you tune the engine lean or rich... its always "proportionally" lean or rich... It runs best, IMO, when either stoich or just slightly lean. In rich form, its SUPER rich at idle, but produces a ton of top end power, which is great for my racing project cars
The car has been tuned and retuned, including dyno time, over the last several years. To the point I couldn't get anything else out of it. The only things that were having an effect on fuel economy at that point were how I drove it. The car has very predicable fuel economy... when I was driving 80% rushhour highway miles I was getting a straight 30mpg, now that I'm driving 100% city miles down now to 25-26 (I want to bring that back up to 30), and mountain drives (@ 5000-6000 rpms in 2nd and 3rd gear yielded a low of 24mpg). Since I don't spend a lot of time on the highway, I have an unconfirmed return of 40-45mpg driving from Denver to CoSprings and back