some, or maybe even quite a few, people here do in fact convert to OBDII from OBD1.
The "reason" is that the specific Toyota tuning in the original OBD1 ECU's is of some concern to some people who believe that there is a lean a/f region in the midband rpm range where the stock turbos transition from #1 to both. If you believe that, you would be convinced to go to OBDII where this tuning was altered. All things considered, I am not a believer in this legend but make up your own mind because I see that in the last couple of years more and more are jumping on the bandwagon.