First Welcome to EM
Nice Classic Malibus! You don't see many on the road in that good of shape these days. My Mom had an '82 Coupe with the 305 -- it lasted quite a while in the family.
It looks like Malibu4 has some potential when complete -- I bet you can get those numbers up.
On the Cav -- I bet you could crack 30 pretty quickly. I've driven a few of the 2000-2005 automatics (rentals) and got about the same, unless driven on the highway mostly and got up to 32-24. What is the typical kind of driving for this car?
The 2.2L has some abilities to benefit your mileage. Exhaust is a hot topic (pardon the pun) for mileage -- a word of caution: too much flow / wave resonance and you may loose some low-RPM power, which is where the best FE is made -- especially on automatics.
I might suggest experimenting with warm-air intakes (I know it's sounds nuts, but some previous race tuners turned EcoModders ended up with results -- depending on the model -- specifically Saturn owners. With GM it varies).
Check out the mods and see what works. Best FE to ya, and enjoy!
RH77