This is a protocol for amplifying very large amplicons that are high in AT. I developed in order to amplify the 8.2 Kb region containing the promoter of Arabidopsis FT which is approximately 70% AT.
In my hands it worked reliably with an 8 Kb amplicon (DeBono notebook 1, July 2010) but can be easily modified for longer products using more dNTP and optimized template concentration.