so i baught a civic with a ls vtec guy i baught it off he said it was built red line is at 9500 so im sure it has difftrent pistons kus the stock ls one would of blown by now lol but it dosesnt pull like a lsv should the vtec pops in hard and all but the motor is fully built he said head has skunk 2 spring n retainers port and polished head and crower cam gears and skunk 2 camshafts block has high compression pistons not sure wat kind but it should pull alot harder if it did have all that ..... i raced my boys del sol with a gsr tranny and ls motor and i bearly pulled him and mine is a gsr tranny and supposibly built lsv could it be the motor is not fully built or maybe it needs to be tuned???

 

might just need a tune. why dont you just pull the valve cover off to see if it has cams in it? you could also do a compression test to see if it has after market pistons.