I don't think it would make that big of a difference because stock manifolds are not equal and stock motors are made to last a lot of miles. Beside the crank and rods are rotating in an elliptical pattern not a straight up and down motion so it would take a lot more than just a 5% difference to start extra crank wear. Also I think if you got to far of it would make your idle suck because of the constant speed up and slow down of the rotating mass. But thats just my opinion.