Re: 4.3 Power
As far as the ATF and the H20 trick, GM makes a "Top Engine Cleaner" for pre-fuel injected engines, and 3M makes a $30 kit for fuel injected engines that screws into the fuel system and cleans the injector, the intake manifold, the valves, and the combustion chamber. IMHO ATF belongs in the transmission, H20 in the environment. The CMPFI engines are clean compared to the TBI and earlier MPFI designs anyway. If you run fuel injector cleaner every couple of tankfuls, you'll be cleaner than most. OBD-II and Calif. emission vehicles 1995UP have the after-cat O2 sensors, Bosch is the best replacement one you can buy. You could always run a "dummy" set of after-cat O2's.
1989 S-10 4x4 4.3L/700R-4, 3.08s, 31" Sport Kings
1989 Blazer 4x4 4.3L/700R-4 3.42s,235 Sport Tracks
1985 S-10 4x4 Soon to have 3504BM/TH350/D44/14FF, 35" Boggers