You most likely have a small rip in a coolant passage and under boost when the head lifts a little you are loosing pressure and that is the reason for the filling of your overflow bottle.
A car can run fine with a blown headgasket I drove my car for 6 months with one it only blew coolant at 25psi and above I just filled back up after the track. (I was lazy that year) I would fix it asap.
Oldman is right your pulling to much fuel out and that is making your timing go to high and knock up top and now you have a blown headgasket it happens alot with a afc and big injectors. Go smaller or dsmlink or chipped ecu.
I guess I just installed them all wrong sorry guys you do need a afpr. I guess I need to find a mechanic for my 11.3@127 2g and my 10.8@132 1g because I apparently can't install fuel pumps .
I too have had both and done countless others and only had overrun problems with 1gs. I say try it if you have problems overrunning at idle buy a afpr.
I have had 255 and 255hp on a stock fpr for over 5 years with no signs of overrun on my 2g. With that being said my 1g did have some overrun issues with a 255hp.