I have won a couple of sportsmen championships in my street legal 97 z28.
I am retiring from full time racing and have been working on fuel milage while not giving up any more HP than nessasary. I changed from a hot cammed lt4 setup to a custom cam and tune. I was pleased to see the fuel milage increase from 9 in town and a max of 18 hyw. to 17 in town to 34 hyw. I think I only gave up about 20 to 25 hp. Hope to learn more on here.