HF's have a smaller diameter exhaust(it's the smallest of all the CRX's),honestly I'd do everything I could to keep it as stock as possible.Honda had the HF figured out back then and IMO it was really ahead of it's time,they're wonderful cars.
OEM is always best(x10),
I'd rather have a gutted HF cat/stock exhaust vs a Si/DX exhaust with good cat,but I'm in a smog free state..YMMV
FWIW,my 287k OEM cat is still good albeit covered in rust and I wouldn't dare try taking any of the bolts out,but as they say "don't fix it if it ain't broke".
By the way,I get ~56mpg in my HF,which I am very pleased with.(seems pretty average from what I've seen)
What're you getting?
Oh and the 118mpg car was in the hands of a 'Honda Guru' I have a feeling there was a lot more done to that car than what was led on,but I could be wrong...
I've just never seen any other HF get close to what he got...
And he did it with the B6!?
Amazing.