Have someone wiggle the steering wheel while checking the steering shaft u-joint, rag joint, inner tie rods, outer tie rods and rack and pinon bushings. Also, re-torque the steering shaft bolts. could be a steering shaft issue or rag joint Hopefully someone with more knowledge can help you pin point the problem
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Mods-MAc CAI , True Dual Flowmaster 40,3.73 ,T-Lok, 25% UDP, 3/8 Phenolic Intake Spacer ,Steeda Tri-ax, SCT Chip/ Tune