You can try increasing your FP with the regulator if you want but I did and it didn't work for me.
I installed GT40 irons, intake, headers, roller rockers, etc. and had the surging. Do to an engine fire (due to a fuel line which wore through due to contact with the frame), I rebuilt it with the '89 harness and MAF. After this I never had the surging problem again. Although there were many things I probably didn't try to cure the surging, the FP regulator is something I did. Sorry for the bad news, this is only my experience, maybe it will work for someone else.
------------------
'88 Mustang GT-GT40 Iron Head Engine, Kenne Bell SC/FMU, AOD
www.geocities.com/rayscopes/RaysStang.html