The lean burn model started from the 2002 Civic HX it was also only available in a Coupe the the 2003 Honda civic hybrid, the Ultra Low Emission Vehicle (ULEV) emission rating is where people gets lost as some review just say ULEV engine,
Honda say so 2003 Lean burn and a few reviews too.
Honda Media Newsroom - Honda Automobiles - 2003 Archive - Honda Creates New IMA System For 2003 Civic Hybrid
My 2003 hhc1 can get lean burn almost anytime. my dash command don't goes to 15.1 but it's peg at 1.4.1 and my fuel flow drops to think it's was 0.7 GPH.
If You just let up 1/2 throttle in first, second and push again, its moves out in a better mpg range a light trottle touch . you can get 52 in part city this way about 5 stoplight.that a cvt.
Get a 2003 try to get one that hadn't a update, as that why they lost the law suite, in back toning down the ima performance to extent the battery life.
Many felt this downgrade back then. Mine has no update a gem

All stock, refresh my ima battery too. My way.
had a friend who had the 2002 Civic HX lean burn he was touching 60 mpg
hwy.but the 2003 can touch 81 mpg hwy with mods.
The 2003 was a record sold years, next to the pruis then it's was as good as the early pruis, it's not a collectable, they have now reach the 100k + miles ima battery life range and extension, so logically half feel safer to sell now, opinion poll com rated the 2003 5 stars.they are well build cars for the money.
Her in Honolulu I wanted a pruis 4 years ago but could not get one for 10 k so settle for a hhc1 and waited for 4 month till one came up, he wanted 9,400 I got it for 8,400 out the door, with new cvt boots added.