HandyMan, I think one of the basic benefits of switching to the 8625 PCM is tuning. Because the baud rate is so much faster, you get more data points, making tuning easier. The $0D masks are decently documented, and like you said have the added benefits of doing things like computer control of cooling fans. Dave W. is one of the good guys on this board, and is a really knowledgeable tuner. If you want to get into getting your S10 tuned properly, grab a copy of TunerPro RT and start learning it. OBD1 may be archaic, but there is a lot of support for it, and it is much less expensive to tune.