1st time firring it up!- steering goes back & forth on its own...

[Z06vette]

Violently! I had rubber gloves on & it almost took my fingers with it. Never seen anything like it. LS1 PS pump plumbed into ford cobra rack & pinion. Even if I had the lines crossed, I can't see this happening. Bad pressure valve in rack? As long as you dont touch the steering wheel, its fine. The slightest turn in either direction and the wheel violently rips left, right, left right. What did I screw up?
Thanks for you help.... sorry about the typo in the title, i cant fix it
Scott