I've had a little experiance with GC rich templates, I suggest tyrying
some of the following.
1. 5%-10% DMSO in your reactions.
2. 7-deaza dGTP at 25%, 50% and 90% to normal dGTP
3. Initial denaturation for 5 min at 96 deg, and cycle at 96 deg.
4. Try pfu polymerase, it allows you to cycle at higher temps which is
important to denature GC rich templates.