The stock ECM timing and fueling map leaves much to be desired. Running larger injectors will decrease duration, but they won't give much more for flow. But having built a bunch of towing rigs over time I have yet to find a larger injector that fixing the EGT's. The higher EGT's tells me that the timing is too retarded across the board. When towing you need a programmer to get back some of your lost timing that you loose with the larger injectors. Its easy to advance the timing and duration with larger injectors, but the stock timing leaves much to be desired.
EDIT: Larger Injectors will still flow the same amount of fuel as meter by the VP-44. Without a programmer you can't compensate for the added fueling. Usually these injectors are also popped lower to allow for more flow, and sooner poop off. This just exacerbates the poor map.
EDIT: It looks like Mike already answered it in a better way then I could.