holley power valve

hey my cars started runnin really shitty at low rpms and backfiring out the carb like crazy. its a 318 with a holley 650 on top. it runs good a mid-high range rpms and i didnt touch the timing so i dont think its that. i was talkin to some one and they mentioned the power valve blowing out on backfires and im pretty sure its blown (i tested it) could this be my backfiring problem or is it sumwhere else thanks for ur help i really wanna ge this thing on the road so badly