My friend has a 99 with a custom burned SuperChip, exhaust, ram-air and nothign else as far as I know and on D.O.T's not sure of the exact size has went 12.8 @ 106, 13.0-13.1 @ 104mph are the norm, not bad for a 4700lb truck? He is sponsered by Superchips and burns them for SuperChips out of his house for Lightnings.
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My Ride Check Out My Site 91GT, Holley SysteMAX II Kit-Heads 2.02" x 1.60",Full MAC exhaust 1-5/8" Long tubes, 2-1/2" O.R H-Pipe, 2 1/2" cat back, 12" K&N Filter, RNH PERFORMANCE Ram Air, Ron Davis Radiator, Full Suspension,3:73's, Welds, Best on new motor-12.60 @ 108, no traction 1.98