I run that turbo on my car with ported anti surge housing. I made 504 rwhp on 16psi pump gas, timing 16*, 9:1 cr, bv heads, 3.9l engine, locked converter, 210/218 112* .500 comp cam. When I choose this turbo I looked at the 62-1 for comparison. I have no info on the ta cover but would speculate it isnt a restriction until over 600hp.