Collector Extension Gains

Anyone here ever added collector extensions and actually lowered their ET ? As im running out of cheap ideas to make up the last tenth i need for a 6 second slip i made these yesterday .I have read lots of tech articles about lowend torque gains on dyno pulls ,but has anyone really seen anything on a strip from them.It was kind of a pain to make these ,cuz my headers have no flanges on the collector.I had a guy at a muffler shop flare one end so they would slip over and i welded sum ears to them and the headers so they bolt on and i can remove them if they dont work .I havent ran it yet ,but i can say the SB seems to be more crisp down low and they actually sound better IMO than the short collectors ...