How to correctly change mean in the distribution?

I computed numerically g-pdf function, where the means- i take points in the grid. When I would to change the mean, i.e. multiply by 1.5*mean, I get completely different results. Do you know why it can happen?

dx = (x_max-x_min)/(n_max-1);
grid_x=linspace(x_min, x_max, n_max);
grid_x = (grid_x(1:end-1)+grid_x(2:end))/2;

g = [];
for i=1:n_max-1

      g = [g; dx*normpdf(grid_x, grid_x(i), sigma)];
  end

In the above example, I just change for 1.5*grid_x(i).

Thanks.