You'll have to excuse the brief response as its a little late here, haha. I'll give it some more throught tomorrow. Off hand the only thing I can think of is that you set your epa while the car was on the bench, not on the ground. Make sure its "block to block" with weight on the wheels, touching the ground.

If youve done this, and the car still has more steering one way than the other under power, make sure nothing is binding up. The bearings, the cvd is put together properly, etc.

Maybe if you want to post a pic or two of the car so I might be able to spot something that was overlooked?