My first attempt at increasing the sprue width and deepening the gates was done with a dremel tool. This did improve the mold somewhat. I friend of mind took it to his machine shop and did a better job. Now the plastic flows through much better and I can shoot at any temperature without the sprue extender. The gates at the tip of the cavity where the plastic runs in at was probably the issues just widening and deepening these a little should do the trick without widening the sprue itself. I was also told increasing the vents may also help.
The photo of the modified mold is in the gallery for some reason its not posting.
I can provide a better explanation if you contact me directly Kirk@bassinthehood.com or
text/call Kirk 951-764-3632
I hope this helps.