friction modifier, yes or no?

[fiveohpatrol]

i will be rebuilding my rear end soon and i was wondering if i should use a bottle of friction modifier or not when it goes back together, what exactly does it do anyway? it was put in when i had my gears installed a couple years ago and it seemed like it would spin both tires more often than it used to, but someone told me recently that it actually HELPS the rearend slip and not to use it, what do you guys suggest? and where can i get a good rebuild kit and what prices am i looking at, thanks alot

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88 Notch, 3.73's, Ported E7's, Explorer int. w/ ported lower, pulleys, 1.7RR's, BBK headers, off-road H-pipe, flowmasters, subframe connectors, 65mm TB, shift kit, March ram air ,MSD coil, U/L control arms, 155lph fuel pump, cheap 2800 stall, Crane Adj.FPR, best 1/4--> 13.77@101.35