I got mine free, and i believe it just goes between the computer, and doesnt replace anything, at least i didnt remove anything to install mine, I run a 160 stat and no cats, not sure what it recomends though, dont know if it made a difference, i am trapping almost 100 mph though, so something is helping.
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Police package 5spd 90 Lx, Stock original motor, 3.27grs, BM fan, fms 10.5 clutch, D&D quadrant, and adjuster, ADS chip, 180 stat, mac cai, mac h-pipe, mac subframe connectors, ASP crank pulley, ripper shifter, 26x10.5 M/T sport pros welds. 246 hp according to analyzer 
Race weight: 3,120
E.t-13.57 with 26x10.50's e.t. streets. 1.88 60'
mph- 99.92 mph
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