NO, you guys don't know what i mean.
They look the same physically, but mechanically, the pre-99 uses an o2 sensor (narrow band) where the 99 and up uses an AFR sensor (wide band).
Basically, the AFR sensor is more accurate.
An o2 sensor is most accurate when closest to 14.7:1 (stoich) but the afr sensor is more accurate than the o2 sensor when it's heading away from stoich (say 12 or 13:1) thus making the two systems uncompatible (as well as the computers).

89 4Runner
3" BL, M/T locks, 33"bfg mt, bilstein, Kayline, tubebumper, toyotafiberglass panels
TBI: Elocker,3.4 w/ORS,b+b,S2Sstg2cams,arias pistons,P+P intake,TRDs/c,URDpullies+7th,downey headers,MAPECU2,WEGO WB, SupraMAF,walboro255,stg4clutch, EPaOo2 sim