The mods you mentioned probably netted him 30rwhp over stock.. Depending on the year that could have been between 325rwhp and 360rwhp.. Our cars are already heavy and you said he had a passenger.. By your own admission you were behind him and most likely drafting and we all know that you can sling shot past someone post drafting.. From the story you told this car did not have a cam in it.. If you want to race a modded LS1 you need to run Dan aka Juiced