beeing an ex. 4gen owner i can saythat a MPFI swap is the best thing u can do on the stock D15B2 motor. the 88-91 SI and the 90-91 EX had MPFI.
i dont know if this site has it or not but Honda-Tech.com does for sure. just search "MPFI swap"
u need:
complete intake manifold. injectors,sensors, throttlebody etc.
si/ex distributor. has a third sensor in it needed for the MPFI
si/ex computer. si and manual ex had PM6, auto ex had PS9.
on a side note i have all but the intake for sale