98 vs 99 Nitrous kit???

If you're looking at wet kits it makes no difference what so ever. All years take fuel from the fuel solinoid from the schrader valve. So yes, your fuel system is different than the 99, it's not entirely a returnless system, but not completly like the 97 return style. If you want a wet kit, any year will work.

If you want a dry shot, it depends on the kit.

BTW- just get a NX EFI wet kit, it's the best and safest

Just saw that your sig mentioned a ZEX kit. Those are pretty good and up there with NX quality. The solinoids aren't quite as large as NX and can't support over 125 hp, which doesn't matter for 99% of us.

Anyway, is the ZEX kit wet or dry?