As cosmik said, in GR both mass and energy curve spacetime, so yes, the more energy you have will result in "stronger gravity".
[tex]{R_{\mu v}-\frac{1}{2}g_{\mu v}R = 8 \pi G T_{\mu v}}[/tex]
This is how we describe a gravitational field in GR. The left hand side of the equation basically describes the curvature of space, while the T on the right hand side is the matter+energy you're dealing with it.
This equation is the Maxwell equations of GR since it describes the generation of fields in GR.