i loved the hell out of my 90 tbi/5spd non-ac 523 van.
i averaged 27 mpg at *texas* highway speeds (~75 avg) and would do 33 mpg (!!) if you averaged 55mph.
It ran 18.2@73 very consistently bone stock. To me it felt less slow then it actually was. The very low gearing of the 3.85fd a523 made it feel like a 16-second car from 0-50 so in normal traffic it didn't feel 'slow' at all.
The same unopened tbi motor i was loving so much has survived 1/4 mile passes at 16 psi and short bursts of 20 psi last time i drove it. It is still in one piece although i cracked the block running too little coolant during a hard freeze. I'm going to put those tbi pistons/rods in another block and keep boosting em.