I have had an 86.5 and a 97 D21. My old one had the 103hp z24i and my 97 has a 134hp ka24e. In comparison, my ka24 does pull harder but it's not like it's the end of the world. 240sx versions of ka24's are more powerful, but you gotta find one for the right price that isn't beat to s*** and actually has good compression, unless you want to rebuild it which is just more money.
If I still had a z24i, I would most likely do a Weber carb swap like this...
zer...rsion
An NA ka24de can make 194 flywheel hp with stock internals, a larger MAF, larger injectors, a nice header and some ECU tuning. This would be about 165 at the wheels with about 1000 dollars invested if you can snag the right parts from a junkyard.
The only limit is your money. If your naps-z is in great shape, it might be worth just swapping that weber onto it.