I had my old motor chasis dynoed in 2006 and it was 300RWHP. So if going with the 17% rule thru my M20 I get 351FWHP. Pretty close to the 360HP Pontiac said a stock 400 should be. I've since changed things very slightly and am about to get it pulled again before the summer is over so we'll see if it comes up about the same.