Using the "seat of the pants" dyno, it does feel crisper. I've never checked the gas mileage (with either the 2-bbl or the 4-bbl), so I cannot comment on that. I forgot to mention a Cloyes double roller timing chain & gears were installed during the 4-bbl swap. I also added a MP Electronic Ignition system ~10 years ago. BTW I found my LD4B on ebay ~4 years ago for $113 to my door!